Bear in mind that practically everything that is said about fiddles is bollocks. There is this whole "rare and valuable instrument" mistique. Truth is there are good Strads and Bad ones. The same is true of the copies. Anyway, you can tell a lot about the age of a fiddle by looking at the neck joint.
No instrument is worth x million pounds. Not as an instrument. Maybe as an antique/artefact, but who's going to play something they can't afford to drop?
Anyway even if it is made in cremona/brescia/mittenwald etc it's sound is only really dependant on the quality of the wood, the thickness of the top and the position of the sound post.
And all that guff about the varnish... Oil varnish is exactly the same now as it always has been. Turps and gum arabic with a bit of colour. The reason oil sounds better than spirit is because of it's micro-crystaline structure, which resonates without constricting the wood too much. There's a certain skill to putting it on right, but it's not much harder to do than french polish.
Anyway, as a guide,
good strad et al copies up to £2500 (for a j.t.l) Stainer types/Bourbons etc @£1000 for a good one. Woodier than the strads, a bit louder. Amatis smaller+sweeter, priced as strads Guaneri: as strads Mittenwald (often with carved heads) £500-£1000 for good ones.
There's a lot of good fiddles to be had for £250-£500 though. Or you could just get a Czec "learner" instrument and spend a bit of time fixing the sound post properly.
Oh yes, carve a lot of the spare wood off the bridge and it'll work a lot better. Free your bass up and balance properly though it's whole range. Not too much though, or it will collapse under the string pressure.