They should physically fit fine but you’ll need spacers if you want them sitting flush with the arches. I’m running 8.5 inch wide wheels with et35 and they’re pretty much bang on. A narrower wheel on a similar offset shouldn’t case any issues.
I reckon you’ll be looking at around 15mm to sit them flush with B5 arches, but maybe even a bit more, possibly 20mm. Your best bet is to fit the wheels first and see how much they need spacing out, much easier than guessing.
As you say you’ll also need longer bolts. I’ve bought a few sets from Awesome GTI in the past and always been spot on. The thread length on standard bolts is around 26mm long so just add whatever size spacer you buy on to that. You want M14 bolts.
If they’re aftermarket wheels you’ll probably want tapered seat. If it’s an OEM wheel, they’re more likely to be radius seat.