Sorry but even a glance at the 2010 and 2013 South Sheilds results shows quite clearly that UKIP's support is basically just disaffected Tories.
http://en.wikipedia.org/wiki/South_S...ons_since_2000
2010 Results - 36,000+ voters, 57% Turnout
Labour - 18,900 votes
Con - 7,800 votes
Lib - 5,100 votes
2013 Results - 27,000+ voters, 39% Turnout
Labour - 12,400 votes
UKIP - 5,900 votes
Con - 2,800 votes
Hmm... conservative vote drops by about 5,000... and UKIP vote goes up by about.. well who'da thunk it - 5,000! Dismal show by the Libs and the generally poor turnout made it a fairly irrelevant by election.