EDIT: just realised, i'm assuming you don't want a tremolo.
washburn x50pro is really nice for £300. comes stock with duncans (hey, you could sell them on since you have MMs), buzz feiten etc. really nice guitar for the money.
if you like thinner necks, maybe an ibanez rga121? marginally over budget (maybe £525 or £550?) but a nice guitar.
problem to me is that £500 is kinda in-between budgets... if you aren't willing to go any higher, that washburn i mentioned is as nice as (if not nicer than) about 95% of the guitars under the £500 mark. But to get quite a bit nicer there's a good chance you'd have to go to £700 or £800.
the guitar companies know a lot of people set their budgets in stone at a round figure (er, just like you've done with your £500 :lol: )... because of that they try (gross generalisation, to be fair) to get away with giving you as little as possible for that budget, as they know that a lot of people won't budge on the price, even for a better spec. it's amazing how many people will pay, say, £500 for something mediocre, but not £525 for something which is much, much better, which seems daft to me. then of course the company hopes you'll have to buy the better, dearer guitar from them later.
Not saying you're like this of course, i'm just pointing out what happens a lot of the time. It pays to be suspicious, basically. :)
Anyway, all I'm saying is, be flexible, and don't be afraid to try things over your budget, and under. That's the only way to see if something is good enough to, say, pay an extra £50 for, or if the one at £500 truly is £200 better than the one at £300.
obviously if you are willing to go second-hand, that opens a lot more doors. :)