Please feel free to copy and paste this in an email to your own MP, sign a petition, do anything. You can find your MP by using this link
Dear Prime Minister,
I was dismayed at your inability to directy condemn the US president’s vindication of the use of torture and also your frankly lacklustre and tardy repsonse to his latest exectuive order about immigration controls into his country. Whilst I cannot know what goes on behind closed doors between you I believe you have a duty to outwardly show your own country that you serve, that you do not condone such actions at all, and not just when they affect British citizens (it is already, by the way).
I would politely ask you to cancel the State visit of President Trump until such moment as his Executive Order over immigration is revoked. If you are not able to do this immediately then I expect nothing more than a full and frank explanation as to why not. Please feel free to write to me directly, or make a public announcement.
I look forward to hearing from you