Hi again – thanks for your ongoing support.
Tried following that and got nowhere sadly, still the same boot loop trying the 136.03 and again the 143 upgrade. One thing I did try was the oldest upgrade loader on the page (TPM171E_3.0.208_upgrade_loader) and this met with a very odd result – I ended up having 2 logos side by side as if the screen was half the size but the same behaviour in terms of boot looping!
Got it back to ‘normal’ (i.e. just bootlooping with a single logo!) by re-applying the 136 update but that hasn’t fixed the looping.
Tried now with the latest version (143) and now it just seems to be hanging on the 4 google circles… no glitching, just nothing else. Has been like that for about 10m.
After the upgrade it restarts, I see the philips logo then the 4 circles, I then take the USB stick out. I am assuming this is OK? Before I left the USB stick in and it restarted the upgrade!
Thanks again for your advice and help. I think I will now be looking for a replacement TV though!