I successfully retrofitted cruise control on Tuesday evening. Another job ticked off!
That was one of the compromises going with an SE spec as I do like to use cruise on longer trips.
It was straightforward in the end. I disconnected battery first and left it a while. While I was waiting I changed my brake pedal switch to the 4-pin version.
Then I removed the wheel and airbag. I swapped in the cruise buttons that I’d picked up from a '5 being broken and then refitted everything.
All tested and working on a test drive 
