I used a crowd called syncron.ie in Ballycoolin industrial estate (Blanchardstown area) for an iPhone 4 button replacement. Forgotten how much it was -- 30 or 40 quid -- but they did it on the spot in about 20 minutes. I'm pretty sure they will sell parts as well as do repairs. Sorry, no info on prices, their website appears to be down at the moment. I didn't think it was supercheap but I was desperate and more than happy to find them.
(Mods -- am I allowed mention company name here? I have no connection whatever with them. Seems ok according to posting guidelines #5, #18, but please delete if this is inappropriate).
EDIT: website back -- my repair was 30 quid, looks like yours would be 60 ... [broken link removed]