Cheers for the replies guys.
DV seems to be working OK, or it is still making the correct noises as and when it is required. :) The hissing is quite loud actually as I could hear it over the radio and me driving enthusiastically up a Wales mountain. It isn't completely dead on power, but I went to go past something in a higher gear and it just seems to struggle past rather than giving a burst of power like it should do.
I will try and get a look at it tonight, as I was thinking the fields could have bounced the hoses around a bit.
Cheers