Not on a Lexus but I had a policy with Warranty Direct on my 10yr old AMG. Very good experience, had two claims. One done through the Mercedes dealership for a wheel bearing (being AMG it had to be sent from Germany cost ~£600!) all handled by dealer, no paperwork no hassle. The second claim was through an MB specialist for gearbox conductor plate. Again no hassle.
Warranty Direct's initial (online) quote for the policy was ridiculously high but I phoned and challenged it, they reduced it by almost 50%.. Renewal quote was again stupidly high and again they dropped it when challenged. Always worth negotiating, I also got the limit on labour cost removed.