While I was switching between EAS boxes yesterday, I remembered that the cruise control vacuum has been disconnected at the usual T for err.. quite some time. So I took the opportunity to reroute the long line from the accelerator in front of the bracketry and that made it long enough to connect up again.
Once I had air in the bags again I went for a test drive, wondering if the CC would come back to life. It didn't :(
Have I knackered it by leaving the vacuum circuit open to atmosphere?

I set the CC button on the dash, got to about 50mph and then pressed the SET+ button on the wheel. Nothing happened. I kinda remember a light on the dash as well, but if that was ever a real thing, it isn't now. Is there anything else I can try?

There's no light to show it engaged. Only the light on the CC on-off switch.

Usually it's a vacuum leak somewhere, i.e.

1. Either end of the pipe between brake pedal & the tee.
2. Inside the pump housing. There's smaller 4mm pipes between the motor & the vacuum relay.
3. The vacuum relay itself not sealing.
4. Leaking or badly adjusted brake switch

Best option is to go through the test procedure in RAVE. Also on the later ECU, you can check it using Nanocom.