Guys,
Thank you for your help. I really appreciate it.
I rang the Lexus dealer this morning. They confirmed it is a belt which should be changed at 100k, although sometimes best to do it earlier. Quoted me £250 for that. Also quoted me £500 for an 80k service.
The dealer insists on servicing the car himself which will spoil the full Lexus history, and won't include a cambelt as part of the deal.
He wants £6795, which is quite steep for a 99V. I'd pay that if he included the cambelt and a recent Lexus service but he won't. So, I'll look elsewhere for one. I might find a slightly newer one.
I'm encouraged by the advice and enthusiasm on here though, and I'll keep you posted on what I do end up with!