Update - Komfortblinker fitted. Blink blink blink.
Straightforward job, took me about 45mins from start to finish, only really made fiddly by the limited access - child hands would help!
Firstly I disconnected the relay and extracted it from its holder and attached it to the CumCartec loom outside of the cubbyhole, but then I found it was not possible to relocate the OEM relay back in the holder and stow the additional CumCartec relay. So I unplugged it all again, put the OEM relay back in its holder, connected the CumCartec loom to the OEM relay PLUG, then plugged the CumCartec loom into the re-seated OEM loom and then routed the CumCartec relay round down into the void space on the left, which seemed to work.
Putting the cubbyhole back in revealed I need to do a bit more cable wiggling, double-check the relay connectors were secure, and then all back in nicely.
The supplier dispatched it quickly too and its a quality part so no worries there.
Nice little mod.