That's not an IS Hybrid - it's the HS250 hybrid - a bit of a parts bin special using parts of the FWD Euro Avensis, the four cylinder US Camry engine and Prius hybrid technology. It's not coming to the UK.
Talking to a guy from Lexus the other day they are planning to have a full hybrid line up by 2012. The LS460 is being dropped in the UK, leaving the LS600h only, the new RX is hybrid only, the GS will be 450h only, and the next IS will be dropping the diesel and going all hybrid as well.