All the above applies!
In truth, it seems a bit steep, BUT, you could spend months searching out a better deal and that time is probable best spent riding.
Engine capacity is pretty much unimportant. If you call John Lampkin (search Beta UK), he'll tell you straight away if you are concerned.
Be careful about all the 'little things' though as they can soon mount up to be a 'big bill'! Just to give you some idea (and most of these things will need doing at some point on an older bike:
Wheel bearings about £15 a wheel
Swinging arm bearings/ bushes about £50
Linkage bearings about £60
Shock spherical bearings about £30 each end
For seals (including oil) about £40
Tyres about £130
All are pretty easy to do, but this will help keep the price in perspective. It is possible to buy a decent honest bike that needs very few of the above for £1k (less if you're really patient); this guy has taken this as a p/ex and may not know about trials bikes. As such, he may not know the significance of any of the above (particularly tyres; those that don't know see 5mm+ of tread and think the tyre has years left; a trials tyre is knackered when it has the same depth of tread as when you bought it, but the edge has worn!).
Control interfaces can add up; you don't want broken levers as the ball end is there to stop it puncturing you in a nasty; £15 each. Bent handlebars are £50 and plastics can cost loads. Even a pair of handlegrips is a tenner and it can all mount up.
As stated above, if you get to water pumps and pistons etc, I suggest you keep looking.
Otherwise, if it is a good, honest and sound bike, a 97 techno is a perfectly decent bike!
Remember, don't let your heart overrule your head!