cruise control

Hi Guys,
My 4.6 p38 2001 cruise control has never worked since ive owned it but to be honest doesnt really bother me i've checked all the pipes etc but couldnt see anything obviouse, but yesterday driving back from shopping on the dual carrige way i flicked it on about 65mph and it worked, changed speed a couple of time and it resumed back to the set speed, i pulled in to get some dog food and when i started up again and drove off tried to put it on again and nothing, any ideas????now its worked once i want it working now, thanks guys.

The P38 has two switches on the brake pedal - One for the lights (Obviously) the other is to switch off the Cruise control and vent the Air Vacuum from the system.....if the pipes are good, the steering wheel rotary coupler is good, and the vac pump is good....it could be this switch on the pedal....

normally when you put your foot on the brake you can hear a pump noise would that mean the switch is working ??

No, if the pump comes on each time you press it, it could mean the Brake Hydraulic Accumulator is getting weak....