Will vented brake discs fit / work in a Willy 3?

... when using original calipers?

I can't remember for sure but assume the original front discs were solid?

I'm looking at buying some vented discs (with internal fins, not grooved, drilled etc) from Ferodo:
http://www.opieoils.co.uk/p-69775-fe...le-vented.aspx

It says compatible with Williams, but in other forums, for other cars, it says new calipers are needed when using vented discs, but doesn't explain why.

Anyone know if I can just fit these to my car without further modification please?

Front disc are vented as standard.

Its only the low spec (below 1.8) cars that run solids on the front.

Okay, that's good.

So those Ferodo ones I've linked above should be a good match?

Been 9 years since i owned a 16v but i think thats the right diameter (259).

Have you tried www.buypartsby.co.uk?

They're pretty cheap for OEM replacements...

Yes, 259mm is definitely the correct diameter for standard discs.