SurferTim:
Need I go on?
No. I believe you when you say it happens, and I suppose this would be backed up by corresponding restrictions in the ToS, but I'm sorry for you having to put up with such restrictive access. Please don't assume that this is a universal problem - it isn't. If your ISP is daft enough to block specific port numbers then the workaround of using different port numbers is so trivial that it hardly needs mentioning. If they prohibit using their services to host publicly accessible servers (however that restriction might be worded) then IMO you need a new ISP; there are all sorts of commonly used services that would fall foul of that and I can't imagine how somebody prohibiting servers in general would stay in business.