You can get the two switches needed from any LR stealer, BUT you cannot get them to sell a bracket to you, the ones on Flea bay have a pattern bracket which is absolutely fine.
There are at least a couple on Flea Bay at the moment - I bought one about 2 years ago for mine, it is easy to fit (with some care)
You MUST disconnect the battery (make sure you have the code for your stereo !!) and leave well alone for AT LEAST 10 minutes to allow the air bag in the steering wheel to disarm (ideal time to have a cuppa)
Then undo the 2 No Torx screws that hold the air bag in place, (on the rear of the wheel, fiddly to get at) disconnect the wire plug and put somewhere safe (afterall it is an EXPLOSIVE device) you will see a 'spare' wire with a plug on the end, usually taped to the steering wheel metalwork, this is the wire ready for the cruise control. no comes the fiddly bit, you have to cut an apature in the wheel case for the switch, just the same as the stereo switch one !!!, I used a stanley knife and a hack saw blade cut in half which worked a treat, when this is done, fit the bracket and the switch, connect the wiring, and replace the air bag etc. Next step is pull out the right hand binicale blank, 3rd one down, and guess what, in the back is again the wiring plug, connect the new switch that comes with the kit, and your done !!!
Try this link, there are loads at the moment, but they can fetch up tp £50+
LAND ROVER DISCOVERY TD5 CRUISE CONTROL KIT GENUINE NEW on eBay, also, Land Rover, Car Parts, Cars, Parts Vehicles (end time 20-Jan-08 22:48:44 GMT)