You value that at 2.5K!! I'd say £1500 absolute tops, so he's put a golf cab front on it & modified some MK2 Recaro seats but other than than it's just a standard MK3 with a sh!tty respray, cheap wheels & generic exhaust!
I like what he's going for with the mk4 conv. but the 'cracked' paint doesn't sound good, especially if it's a custom bumper - read. filler!
It'd take the larger part of £1K to get it looking right, repaint door, fix & repaint bumper etc.
I'd ask for some much better pictures, taken in the daytime or better yet go see it!
Quite high mileage as well!