Play stupid games, win stupid prizes.
The UK Parliament, which has determined them as being a terror group (not just for 'protesting', do your research as to what they're also connected to i.e. support of Hamas which is currently an ILLEGAL practice in UK law). If, knowing this information, you continue to voluntarily associate with them, you can't really expect to be treated any differently to how you are by the legal system. At least until Palestine Action are no longer declared a 'terror organisation' by the government and Parliament (which is Sovereign).
TL;DR, If it's legal, go ahead exercise your legal rights. The second it's not legal, as determined by our democratically elected Parliament, you stop associating with it, or face the legal ramifications.