The biggest problem with a £200 budget is that even though a playable guitar can be had for that amount, the pickups will be total rot unless they've already been upgraded.
Going for a 2nd hand guitar is a plus point at this price since it's most likely had a setup, maybe even a fret-stoning to get it playing right. Also, in the case of the SG there are a pair of awesome pickups in the guitar.
If he could walk out the door with that Warpig'd SG for £275 he would have an amazing platform for the majority of metal. Surely he can beg/borrow an extra £75.00 ???