There do seem to be some hot button local issues down there that will be very important to the outcome. The Huhne Affair and now all this business of Rennard and Cleggs leadership must play a part in some voters switching from the LibDems, but who they will switch to I am unsure. The conservative MP did herself no favours over the whole "I have a gifted son who is too good for a local state school", and has been somewhat -absent-from the debate.
I think UKip might have a very good chance here - by all accounts, their candidate has been pretty good. I personally doubt Labour will be able to gain enough votes to make it as close as Gromits prediction, but we shall see :)
This was the result from the last general election in 2010
http://news.bbc.co.uk/1/shared/election2010/results/constituency/b57.stm