Four plastic prongs on the button have to be pressed into place on the horn. The problem is Land Rover doesn't sell just the button. They only sell the complete assembly. To install it you need to remove the airbag. None of this is very difficult but if you're not very handy and don't have good, long torx sockets to remove the airbag, it can be.
Now, of course, they may go on eBay and get an aftermarket horn button for a few bucks but it may not match. I've had a truck come in for parting that had the original button on one side and an aftermarket one on the other.
Aftermarket:
Land Rover Discovery 2 Series II Horn Switch Button Cover Cap New Design | eBay
Original:
Land Rover Discovery 2 Series II Horn Switch Button Cover Wiring Assembly New | eBay
Now, of course, they may go on eBay and get an aftermarket horn button for a few bucks but it may not match. I've had a truck come in for parting that had the original button on one side and an aftermarket one on the other.
Aftermarket:
Land Rover Discovery 2 Series II Horn Switch Button Cover Cap New Design | eBay
Original:
Land Rover Discovery 2 Series II Horn Switch Button Cover Wiring Assembly New | eBay