There are a couple of major airports in the U.K where they appear to not tolerate spotters at all, altho' one has a "visitors centre"
If you're referring to Heathrow, the Visitor Centre there closed more than two years ago. The only concession to enthusiasts nowadays is a rather odd "grandstand" which offers only a marginally better view than standing at ground level.
It beggars belief that the operators of one of the world's largest international airports can't get their heads around the idea that, like it or not, people are going to want to come and look at the aircraft landing and taking off, and that providing them with at least some basic facilities (say a cafe, or as a minimum, loos) might actually be good for the corporate image.