Well, managed to get time to do the indicators mod, but have to say I'm not overly happy with the result.
Okay, the blinking is now instant, but I just don't feel the power output from these is close enough to the outgoing halogen bulbs to warrant keeping them.
If anything, the colour is slightly duller (most likely due to the fact that the light being omitted from the LED is white and the amber housing it sits in is filtering out the majority of the spectrum, where as the original halogen was more yellow to begin with, and as such appeared brighter), so it's more of a dim orange. This is proved in the fog where the LED is far superior to the outgoing halogen where no filter exists in the housing.
Personally, I'll take the brightness over on-off duration for the indicator until such time a suitable replacement is identified. May investigate other options and feedback results!