Right....I phoned around several Lexus dealers yesterday. The consensus is that the battery is designed to last the life of the car, not the 8 year cycle that some have said. Also all of the main dealers I rung said that they have never replaced a battery on a LS600h....ever ! I think I got through to 5 or 6 around the country yesterday. The costs if anything did go wrong ranged from £3000-£4000 fitted and inc vat.
I'm also in the process of researching battery repair as there are several companies that do this in the UK now
Hope this helps people
Thanks
Jon