This is no longer the issue all this has been replaced so something else is the cause but what ?
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If you have replaced the lines, pump and CC ECU and if you can hear a click when you press the switch that means the switch on the steering wheel isn't faulty.
Disconnect the line at the T piece and see if the line going into the cabin holds pressure, if not then it might be the cutoff switch under the brake pedal.
You will find there are two switches under the brake pedal, one is for the brake lights and the other is for the CC. pull both of the plungers out a few notches and see if that fixes it.
You don't need to remove the switches behind the pedal, just press down on the brake pedal with one hand and pull the plunger out a couple of notches, the plunger is on a rachet.
When you release the pedal you will here a couple of clicks as it resets itself.
I had this issue 3 or 4 years back, brake switch was the problem, from memory the lip on the plungr had broken, i glued a washer on, with no problem since, i'll have a look tomorrow and post a pic if u need
Check your brake lights. If any globes are out then the cruise control may not work. I was told this after I had problems with mine. good luck.
Attached is the instructions, with mine the plunger top was broken so always releasing the vac
Thanks mate that helped allot.