This does the rounds quite often with people on both sides massing armies ready for an all out pre-emptive strike upon the other camp whop they consider - HERETICS!!
Consensus seems to be: If you are pixel/grain peeping then you can see a just barely perceptible softening, however since there is absolutely no application of a whole image where this BPS would be noticeable then it becomes a mute argument.
I have always used UV filters from day one, I have smacked them up, scratched, thrown them away when the got cleaning marks, they to me are disposable after a few years of use, the lens however has always had a crystal clear front element.
I had a drunken bride throw champagne at me, she slipped as I was about to take a photo and went a over T with ensuing results of flying drink, no time to clean, I just whipped the filter off, took a few frames, then retreated to clean and put the filter back on.
So my opinion has always been, there are far more pros than cons, so for £30.00 why not go for it?