Hi Herbie,
Thanks for taking the time to answer my question in such depth, I really appreciate it, learnt a LOT! I don't think I'll be put off by this as I've heard that these cars are super reliable and the chances of having a hybrid failure are quite slim.
FYI, I'm looking to buy a used 2006/2007 Rx400h with between 100-165k miles (as long as they've been serviced properly) as I've heard that they can normally get to 250k miles without too many headaches/maintenance issues.
Thanks again for the info!