CC only valid for Marriott weekend packages and only at UK hotels, if I remember rightly.

Hilton is more interesting. You can redeem CC for Hilton hotels in the UK and some European countries. AND you can get suites, executive rooms etc! The Euro hotels are: Hilton Paris (not the new one, I think, its the Arc de Triomphe one), Hilton Brussels, Hilton Barcelona, Hilton Milan, Hilton Amsterdam, Hilton Luxemburg, Hilton Berlin, Hilton Munich Park and Munich City, Hilton Istanbul, Hilton Dusseldorf.

You can check the Tesco rates by using corporate code PR20TC on hilton.co.uk - this brings up Tesco rates, although you can only book on the phone. Remember its £1 of Tesco vouchers (£1.87 of Marriott points) for £4 of Hilton night, so when you buy from Marriott you are effectively paying 47% of the web rate shown. However, the Tesco rate is often not competitive with other web rates so you need to make a judgement based on the rates available.