Hi Neil,
Like what you done to the car (very professional work)..
when i bought the car i did ask the seller to call Lexus dealer in Manchester check if the cam belt changed as indicated on the log book. was so please drive all the way back from Wigan to Birmingham. To my shock to discover the belt already badly worn n might snap anytime (did post picture here) as all say it's advisable not to drive the car.
won't hurt to sneak a peek now and then