Right, here's an update... With pictures...
^^^ As you can see it has a relatively old dash, so definitely JTAG season I feel
^^^ Opened it up as the sticker was void, but inside is 100% stock. Weird.
^^^ To preserve it's longevity I fitted the newest heatsinks using Arctic Silver 5 and kept the x-clamps. IMO they do their job well, so why change them. Even MS still uses them still.
I also added two small heatsinks to the ANA and South Bridge chips. Reassembled, powered up, played Burnout Revenge for 3 hours and it's all good.
Anything else I should do to keep this thing working for all eternity?