Thanks though I seem to have fixed it (fingers crossed):
According to most the only way to cure it is either clean connections or replace switches which involves removal of steering wheel and airbag etc etc. I didn't fancy all that hassle so I looked down the sides of the switches and could see 4 very small square holes. These holes are just big enough to get the end of a small straw down so I sprayed down each one with contact/switch cleaner. This I did a week ago and normal operation was resumed instantly and has worked fine ever since at all speeds... Worth a try for a 5-minute fix!