Looks like the 2015 election was fairly predictable. In general, the more money you spend, the more votes you get.
If you remove UKIP the R^2 goes up to 0.99 – all that free publicity the UK media gave UKIP really helped them.
(Sources http://bbc.in/1ISUaHL and http://bit.ly/1OxkpFr)
Andy Connelly 