On parts, Autodoc (EU based) are good for most service parts. If you need OEM Toyota, Amayama have the online catalogues to find the genuine part number and will ship from Japan (postage starts at about £20 and takes 2 weeks, add £12.50 import fee and VAT if the order is above £135). Once you have the part number from Amayama it's also worth searching eBay, Toyota Direct Parts (you can submit a request if they don't list it) and calling your local Toyota dealer for a quote.

On service information, there are official service manual CDs which are very comprehensive. They're mostly HTML files and images - I use Firefox browser with its inbuilt translation which makes a pretty good job of translating the Japanese into English. The Techstream dealer service software is also widely available online (there are knockoff 'MiniVCI' cables available, but I'm using a Tactrix Openport clone which seems a bit more stable). You can select Japanese models but use English for all the prompts - especially useful when it's stepping you through a procedure. You just need a garage who is used to thinking out of the box a little. Many garages are all about throughput - they do regular MOT repairs all day long and it's all priced up on the computer - it's not worth their while for anything that falls out of their usual pattern, eg parts aren't available from their usual supplier. You need someone who is willing to take the time to do things a different way - either someone with JDM experience or an old school village/backstreet garage who is willing to do things differently, and perhaps have you hold their hand if needed.

I think the hisat015 and 016 diagrams are for the heating, cooling and air con systems. The Hybrid cooling pump comes under the hybrid system.

Yes they are for the ATH10 hybrid from the official Toyota manual, translated from Japanese. There is slight differences from the early models and the face-lift models 2005 but that is indicated on the diagrams.

Thanks to you also, sir - I'm getting some excellent help here, in advance of my inspection.

There are plenty of dedicated parts suppliers either independents or even some Toyota dealers, in fact Toyota sell service parts on eBay. The only electrical problems that crop up regularly are the powered sliding door which is in fact a bowden type cable that breaks up and jams the motor inside the door, a quick solution is to cut the cabel and open/close manually and the ballast units for the dip headlights but they are an easy fix as well