i too have had this, (i have posted on the subject)(
http://www.volvoforums.org.uk/showthread.php?t=88930), the microswitch will cost around £14, but, i tried it and it didnt cure it, wiring is ok, so the local dealer said it will be the cem, £400 + £250 (for programming) + fitting approx £800 just to open the boot
although i will give the previous posters idea a go first lol