Well, I thought I'd report back on my progress. I did look at a Blues Cube and it was fantastic but at almost £100 more than the Orange, it was just too expensive.
The Fender Champion 100 is undoubtedly a hell of a lot of amp for the money, coming in £120 less than the Orange with double the number of speakers, almost double the power and weighing less. What's more, the tones are very good too. It has a lovely clean channel on it and the models on the drive channel are all good too with loads of gain available on the 'Metal' setting. Unfortunately, there were things I didn't like about it. Having a 2-button footswitch with one of those buttons just turning effects on and off while the other simply moves from 'Clean' to 'Drive' is ridiculous. With quite a few models available on the Drive channel, this means that to switch gain settings at any time in a show, you have to do it manually at the amp or use an external pedal and that just seems silly to me when for the cost of a few more buttons the amp could have done so much more. The other problem was the tone. Although listened to in isolation it was very good, it was noticeably digital sounding when directly compared to my Blackstar. Now I didn't expect the tone to be a match for a valve amp but in this case the difference in quality was enough that I couldn't entertain the notion of such a change. On to the Orange.
Physically it looks tiny compared to the Blackstar, which is unusually big for a 1X12 and though I've read reports saying it's heavy for a solid state amp, I found it positively featherweight compared to the Blackstar. Build quality appears to be excellent. Good start.

I tried the Clean channel first and was pleasantly surprised by the quality of the tone. It was clear and warm and while it didn't have the richness of a good valve amp, it was still good enough for me. That's partly because I don't use the Clean channel much but mostly because I've never been that struck on the Clean channel on my Blackstar. Treachery as it may sound, I preferred the Clean channel on the Orange to the Blackstar.

I then set the Clean channel just to the point of break-up and asked the shop to give me an Overdrive pedal to put in front of it and they brought a Marshall GV-2. The result was reasonable but hardly spectacular and I was left somewhat disappointed that I couldn't get a better crunch tone that way.
Next I tried the Drive channel and I was initially disappointed. On the Blackstar, setting the gain to '3' gives me plenty of distortion for a good AC/DC sound but on the Orange the sound was still pretty much clean.

Instead, I moved the gain to maximum and tried again. This time there was plenty distortion and for the first time I noticed the 'fuzziness' I'd read about Orange amps in some reviews. It wasn't bad at all and in a way I quite liked it but it was certainly different to what I'm used to.

Next I tried moving the gain to about halfway and found that between 50% and 75% is where this amp likes to live. The distortion was really quite impressive with very good articulation and what was even better was that the GV-2 seemed to work rather better on the Drive channel, giving me the extra distortion I might want without the fuzziness.

The sales girl told me that she owned one of these amps and she used hers that way too. At this point I decided that the GV-2 might just not be very good so I brought out my Carl Martin Quattro that I'd taken along just in case. Hooking this beauty up to the Orange made a huge difference. Engaging OD1 from the Quattro on the Clean channel produced a drastically improved result and OD2 just gave me more distortion with the same good quality tone. Ironically, I've never liked using the overdrives on the Quattro with the Clean channel of the Blackstar but on the Orange it was a revelation and I loved it.

Encouraged by this, I returned to the Drive channel on the Orange with the gain set at 50% and engaged OD1 on the Quattro. Mmmmmmmmmm; a REALLY nice sound and once again, moving to OD2 on the Quattro did nothing to remove the quality of the tone. Smooth, very articulate and very 80's Metal in style but with more gain. Once again I found myself very impressed

Next up was to do a back to back comparison with the Blackstar and this is where it got tricky. God I love that amp and in the cold light of day, the tone from the Blackstar was definitely superior. It had more depth, more richness and more complexity in the tone compared to the Orange

BUT the Orange amp did have some redeeming qualities.

If you approach the Orange looking for a perfect valve tone, you might be disappointed. It certainly has some valve-like qualities to it but that doesn't make it a direct substitute for valves. If, however, you approach the Orange just looking for a good quality tone that is its own thing then I think you may be pleasantly surprised as the tone is really good. It has a lot more to it than solid state amps I've tried before even if it doesn't quite have the harmonic richness of valves and to be frank, I liked it. Furthermore, strange as this may seem, the Carl Martin Quattro seemed to work even better on the Orange than it does on my Blackstar and I found that using it with the two channels on the amp set up how I liked them, I could end up with six very useable tones whereas I can't get that many on the Blackstar. I have absolutely no idea at all why that should be the case as I know nothing of electronics and I would have thought that effects from Carl Martin would be tailored more for higher end valve gear but to my ears it just worked better with the Orange.

Decision time. On the one hand I really struggled to get past the fact that the ultimate tone on the Blackstar was better

but against that, the Orange was smaller, lighter, worked better with my primary pedal, had a more consistent tone in relation to volume and I'd no longer have to fork out a chunk of cash to replace valves! On top of that, I DID like the tone and while the valve amp may have been superior, it wasn't by anything like as much as I'd feared. In conclusion, I took the bull by the horns and decided to make the change. I'm part exchanging the Blackstar and even including the optional footswitch with the Orange, it's still costing me very little to change. I didn't have my own amp with me today as I used one of their Blackstars for the comparison so I'll be picking it up next weekend.