Update: Whilst waiting for this Thursday to come when my local garage has the time to re-check and investigate further, I am only using the car to travel to work and back (6 miles each way). So approx. 70 miles all in. Did not use it Saturday. Washed it Sunday (have to keep it clean - it's a Me-Thing). This morning, Monday it would not start - just turned over & over, on the third attempt it bit but sounded as if only running on 2 pots, switched off and left it on the driveway - contacted the garage man who's going to check it out tomorrow. He is only willing to spend a couple of hours on it and then leave the decision to me.
I am getting ready to contact my local Lexus garage and face what I've been dreading. ££££££££££££££££££££££££££££££££££££ Oh well if I want to run my Dream Car then I have to accept the financial demands. Hopefully it will not be totally bad news - I've had 4 years trouble free, but after all it is only 8 1/2 years old.
To answer Noo Bie - I did check with Lexus when the read-out reported the 2 faulty sensors and they said it would cost around £630 (including parts & VAT) to replace them.