I have since found out that you cannot purchase a bush on its own and the bottom wishbone has to be replaced completely, a new one is about £200+vat from Lexus, or second hand for around £75.00.
But be careful the toyota supra has same wishbone so breakers might be selling this too you as a Lexus part.
Andy the £1k seems a bit heavy might be better to buy the bushes new or second hand and have them fitted by your own local mechanic if posible, you should be able to do the job in half the dealer quote.
Remember the tracking will have to be rechecked and aligned.
Best of Luck
Awais