Phoned the Lexus dealership again this morning and they confirmed it is covered when pushed about the 140,000 limit, they are sending me a booklet out to read, looks like this will be the way to go.
Interestingly my Lexus is 10 years old on the 30th April and if the extended warranty is taken before then it will be covered until it is nearly 12 years old or 140,000 miles.