O2 are pretty decent for coverage. It depends on your area though and if you haven't been with them before, pick up a free sim from them (they give them away through banner ads on various sites). That way you can be sure you got coverage as the last thing you want is to sign a contract and have poor coverage.
Service wise, I never had to call them when I was on O2 so I can't really comment on that.
As for the RAZR V8, it is available direct from O2 online for £20. There are threads on here covering the V8
here,
here and
here (review). Hope that helps