I've finished off the indicator retrofits by converting the rears - Unfortunately there's not a great deal of choice in the W16W amber size, which means there were no bulbs with inbuilt resistors; For testing, I grabbed some cheap ~£10 COB LEDs from Amazon, on the off chance the inbuilt CANBUS resistors would prevent hyperflashing, but unfortunately that wasn't the case.
As such, I also got some 6 Ohm, 50W Resistors - These have worked perfectly to prevent hyperflashing. I'll probably upgrade the LEDs to a more robust bulb in the future, but these certainly do the trick, being brighter than the filament bulbs, and having instant on-off.
The resistors on the bulbs do get fairly warm, with a several minute use of hazards getting the resistors up to about ~85c before they level off.
Whilst in the back, I've also changed the previous LED reversing lights to OSRAM W16W bulbs; They give a little more output than the previous LEDs, but mostly give a perfect white which matches the numberplate LEDs, and are of generally better quality.
And the best part, Instant on/off:
For good measure, the reversing lights: