Got my car back, good as new....
...plus the DRLs and exhaust tips are on.
ECU was saved, four relays were beyond saving and were replaced. The LED indicators and sidelights didn't get fitted. The indicators take their power from inside the headlight cluster to a terminal on the side of the bulbholder, which isn't compatible with the error cancellers I had bought. Meanwhile, the error cancellers for the sidelight LEDs couldn't be found anywhere amongst the kit I'd left in the car, so I just said to leave them as they were. Of course, I found them hiding under some other junk in the boot as soon as I got home. They can keep until the next service and MOT.
Final bill for everything, £362
Here are the DRLs:
and here are the exhaust tips: