As mentioned above so long as you have full service history and the mileage and Mot documents all line up you know you have a good engine as they are not the weak point. I caveat that by saying there was/is an issue with the earlier models and the fibre overdrive washer wearing which costs a fair bit to replace. You also need to make sure the turbo is in good condition and the only way to really check this is to check for fault codes that may be stored on the ECU. This can be done with a machine or by Toyota otherwise you have to short a couple of pins out and then count the flashes of the engine management light to get the corresponding code. If they localish to Berkshire then let me know as I have a machine to check for codes if you want to use it.
As mentioned the AHC needs looking at and at the same time make sure the Satnav and AC controls are all working. As they are costly items to replace/repair.
If the owner says the AC just needs gassing then get him to do it prior to purchase as if one of the rear ac lines have gone its big money to repair by Toyota so use this to bring down the price by a good £1500 even though you can do the repair yourself for £150.
Rust is the main killer of a good car due to road salt. Check the underside, all wheel arches, inside the rear quarter panels by removing the rear light clusters. Above and around the windscreen, the top and bottom tailgate sections (these are replaceable by Toyota through warranty).
Make sure all the numbers on the 4 doors, bonnet and top and bottom tailgate are the same otherwise you know a panel has been replaced.
Steering wheel motors up and down and in and out, both tilt and open and shut of sunroof if you have one.
I think that’s about it.