Update for anybody searching : Managed to fix this problem this week and turned out the 2 cruise control buttons on the wheel were faulty - replaced them and now all working.
Interesting Nik, as I have the same issue with my trophy - you select +/-/R/O and the speed/display goes up.
I have a spare set of switches so will try swapping them over. If that doesn't work the next swap will be the squib.