Cruise Control playing up

My euro is getting up to 200,000k's now and my Main Cruise Control button wont stay activated.
I press the main cruise button and the cruise control light on the dash; lights up for a split second and then the button on the steering wheel clicks off.
Does anybody have any ideas what this is and more importantly the cost, before I phone the dealer.

I try and avoid my dealer, after them wanting to charge me $950 for a tow bar installation.

I would spray some electronic cleaner & lube in it( NOT WD40 ) It is what technicians use to clean guitar pots & things like that. Just might be a sticky switch Especially if the car has done lots of kys ..

Thanks for that suggestion. As its the MAIN cruise control switch, it would have been used about ten times its entire life.
I will give the spray a try.

Could be stuffing up through lack of use I would defiantly spray it with a good contact cleaner. Press like mad til it works.

try pull the footbrake up when you turn on the cruise control. if it stays on then the switch behind the footbrake needs adjusting. this fixed mine

Any luck? Mine has just done exactly the same thing...