This is a bit different from your exact question, but you may find it interesting anyway. Although I personally am not specifically aware of people in Britain that supported the colonists, I do know that the American Revolution was a rather unpopular war in the eyes of the British public.

The outbreak of the war came as a surprise to the British people. They didn't know a lot about the situation in the American colonies -- That there was a lot of building resentment, that American colonists could form successful militias using hunting muskets, and that the colonists were indeed building up militias in preparation for a war of independence -- so when the war broke out, it came as a bit of a shock to them, especially when the British army wasn't able to quell the rebellion.

As the war progressed, the British came to resent the fact that it was resulting in heavy casualties of their soldiers and that their taxes were being hiked on most commodities to fund a war in a place most of them had never even seen.

This is interesting to me, because it demonstrates major similarities to modern wars like Iraq and Afghanistan and how public opinion on these sorts of wars has been similar throughout history.