Apologies for the long absence, change of job/house etc etc.
For those that are interested the issue was quite straightforward: A blown fuel pump relay, cost £25,00. (Well done ChrisKaye).
Sadly, this wasn't discovered until a completely new battery had been put in, at which time I thought, well if I'm going to do this then I might as well do that.... etc etc.
The three lessons learnt were:
1) The car will run on battery alone if the fuel pump relay fails, (or at the least mine did).
2) Lexus Tunbridge Wells told me they had tried to charge the battery and this had not worked, (the diagnostic report on the battery that Toytec showed me proved this to be a complete fabrication). I'm can't even be sure they did the inverter as per the recall. I was still charged £150 for the pleasure. To fail to notice a failed relay shows that either they are entirely incompetent or just didn't want to know but I wouldn't have expected to be lied to. The myth of the wonderful Lexus dealership is just that and I will never frequent one again.
3) Toytec in Crawley are excellent however their chief mechanic is a major perfectionist and if you are also this way inclined, (as I am) you may well come out with half your car being replaced and £6k lighter! Still, 20k miles later without so much as a murmur and I'm a very happy owner.
Tom