Hi Rich,
The service schedule cycles through Intermediate and Full services and although the Full services are called 20, (40, 60, 80 all same) and 100 they should be done on age regardless of mileage. So the cars last service was hopefully the 100 rather than the 60.
You can see the details of each service using the link at the bottom of this page
https://www.lexus.co.uk/owners/servicing-and-maintenance/vehicle-service/
The gearbox is claimed to be lifetime by lexus, but some owners dont believe in such a thing and have had the fluids changed, it is possible.
I think there is a group by for some manifolds on the go that might be worth a look, although some owners have found this issue to just be the gaskets and not the manifold so would be worth an inspection before splashing some money. None of the manifold options are cheap I'm afraid.
If you can find something simple to take it to lexus, MOT's are reasonable, they will jump at the chance to do a inspection FOC and find something to charge you for 🙂
H&S is steel so you shouldnt see any issues with that, most lifetime warranties only cover the first owner unfortunatly.