Hi Pete,
I haven't had Beta wheel bolts re-chromed, but I did have some bike parts re-chromed locally the other week - the passenger grab rail, the 4 bolts that hold it to the subframe and part of the gear lever - total cost £60 and the finish was excellent. I'd be surprised if there wasn't a chrome plating/electroplating firm near you, but I'm sure my Sheffield firm could do mail order. Their details are:
Alpha Electroplaters Ltd.
17 Wood Fold,
Sheffield
S3 9PE
Tel: 0114 275 6702
Be aware that if the parts have any severe pitting that this will affect the final finish, as the chrome plating doesn't fill in gaps. It's quite a lengthy process, as the original plating has to be stripped in an acid bath, followed by buffing/polishing, then a layer of nickel, then finally the top layer of chrome.