tube/valve amp you can get in the UK at decent prices is the laney LC15/LC15R. These are UKP £150 -230. they are a very fine amp and have great tone, features like line out so you can run 'em through larger amps. i tried a selection of 15-50 watt amps and the LCs blew away most solid state amps up to 50w. The Pignose 40 valve amp sounded ok to me as well. In the end I went with a Vox cambridge which has a valve preamp and all the features (except reverb) but a soldid state power section...I find the tones fine.
there are many hybrids like this such as the ashdown kidd range.
These types of amps are usually ok for medium gain sound up to LED ZEP,Queen (hard rock) type noises, for Metallica+ you'll need an HM pedal.
Start huntin'
Accuracy,you say? hmm interesting concept..