Im no expert but I would say that if it wont rev past 1500rpm replacing the clutch wont fix it, changing the clutch would just stop the clutch slip, id be speaking to who you got it mapped by and asking their advice if its only happen since the remap.
As far as the clutch goes it seems to be a common problem on higher mileage cars especially when you got stage 2, im looking at my car remapped soon but gonna have the cash in the bank for a new clutch waiting for when it goes (prob from reading post will be a sachs clutch aswell), have a search on here as you may need another item replaced in the clutch (cant remember what it is, as I said im not an expert) but I think it added about another £400 onto the price of getting it changed