I just bought a Pirelli and I'll be tempted get get some for it when the time comes. I could be wrong but the PZero Rosso's are the only ones that have the red Pirelli logo on the sidewall - not 100% sure on this though.
Tyreleader has the Rosso's for cheapest at £70.79 delivered - not sure if that includes fitment, balancing and taking away your old ones though?
Mytyres has them for £85.40 which they say includes fitting, vat, valve and balancing. Doesn't mention your old tyres either.
Kwik fit has them at £85.50 and includes getting rid of your old tyres and all the rest.