Hi Paul,
Junction Block Relay I would buy from Lexus and have a auto electrician fit, and if that doesn t fix it , get a ABS unit from breaker, also important is NEVER take heed of anything Duncan Roberts types, he is ALWAYS negative, he is the devil on your shoulder telling you you are too ugly and your ***** is too small!
Also as boxbrownie pointed out join club Lexus US, best thing I ever did, and I run my RX300 on Fiesta money ( not petrol obviously ), every problem is covered, every DIY job has a picture guide so even the worst home mechanic ( me ) can do it.
Lexus parts are very expensive ( more than Mercedes ) and their hourly rate is huge, You really do have to be relatively wealthy to have repairs done with them ( their Essential Care Servicing for vehicles over 5 years old isn t too bad if you wish to keep your MDSH )
Good Luck
Jason