hi there larkone, thanks for the info.. and link, ive spent half the night and day (or so it seems) searching for the right one and i think ive nailed it down to the denso 234-4626 the sensor is on bank 1 so i presume its cylinder 1,2,3 and its after cat so i think thats what they mean by "rear", also the ebay link seems to tally up as they desribe it as "lower".
This is the one i ordered
http://cgi.ebay.co.u...:EOIBSA:GB:1123
Also i found a thread on the usa club lexus site that had the same part numbers on
http://www.clublexus...020-post10.html
hopefully ive got it right, if not ill order the bosch one from ther uk, i would of just got it from there anyway but i got excited with the buy it now button.. lol