What do you mean by Muslim immigrants? Do you mean people who are Muslims and who come here on an indefinite basis? Or just banning any Muslim from entering the country?
You do realise there are Muslim scientists, academics, students and professionals who come to work/study here for temporary periods, yes? I doubt those will be affected.
If you're talking about unskilled labourers from the Muslim world, I am sure the numbers will be reduced after all of those terrorist events, nothing to do with Brexit though, only idiots think that the EU controls our borders in terms of the numbers of Muslim workers we let in, not including refugees that is.
If, however, you are talking about a complete ban of Muslims, I don't that would happen, it's against our values. How will you differentiate between Muslims and ex-Muslims (those born in Muslim families but themselves are not Muslims, i.e. do not believe in Islam)? And how is the method you're going to come up with is perfect, i.e. no Muslims will be able to cheat through it?