Why not have a go yourself? it's not as easy as it looks. Yes, an anagram server helps start you off, but it won't give you any kind of steer. You have to have an inkling of an idea and try and develop it from there. As an example, there are 104,167 possibilities for the phrase Unleash Britain's Potential, and they only show you the first 500 results, none of which bear any semblance to "Still European Inhabitants". In fact many of the results are just jibberish. Here are the results you get from just typing in "Unleash Britain's potential". They're not much use to anyone!
If you like anagrams and want to see more of mine, here they are. http://www.alasdairmurraycopy.com/anagrams.html
The conservative manifesto ones will be rolled out on Twitter soon.