Piston 25-75 quid , depends on manufacturer , rebore I paid 20. Check if the piston kit includes a small end bearing , this should be replaced as well . Also check clearance on the powervalve especially if it is more than +1 size rebore .
Another thing a few people forget when doing an overbore, is to buy a GENUINE, head gasket, and have that also reamed out to suit the overbore size, personally if you can take the whole engine in to the place doing the re-bore, try to, as they can skim any bits that need doing, and will put it all together for you, so all you have to do is bolt the engine in and it should be good to go, and you'll have peace of mind it's all as it should be.
