Looks don't really come into it,
£100 get you a new set of plastics and set cover.
Make sure the motor dosnt rattle and the gearbox is fine.
Then there are fork seals, bearings and bushes to consider.
If its very tidy and has all the usual extras (bash plate, hand guards) i would say £1250- £1400 if it needs plastics and is tatty £1000 tops
Maybe better looking to buy a 200 exc gs, they were available until 2002 (clear fuel tank) and the main differance is a seperate oil tank so no messing with oil when your out on the lanes
I have had a 1999 and a 2002 (both with autolube) they are a great bike, 125 chassis and a 200 motor , very light and nimble
I had a FMF gnarrly pipe and tail pipe on my 2002 and it gave it more bottom end, also worth puttin a fly wheel weight on them
Cracking bike and now looking to buy a 2008 model or maybe a 250 2008