If you are a dab hand with a drill, small screwdriver, hammer and narrow nose pliers you can do it yourself in a couple of hours. I'm now on the fourth one in two years. Have been going around the car each wheel in turn as one fails. Latest escapade was both nearside ones. You can get them off ebay for less than £50 each and even if you have to pay someone to fit them pay no more than £100 for labour. You will know that main dealers charge £120 plus vat per hour and they are about £140 each for the sensors - the same Wabco ones you can get for less than 50 as I say.