"about what? rentering Europe.
the uk is set up for referendums, There have been 3 since 1975.
Parties do control Their MPS they use people called Whips"

I guess you don't know too much about UK politics.

Here in Dover & Deal we have just elected a Labour MP
When parliament next meets there is nothing to stop that MP deciding to join any other party. The whips have no control. They can only threaten a MP with stopping or hindering his advancement in the party. The MP is under no obligation to take any notice of the whips.

Meanwhile as voters we will have to wait until the next election to take action against the MP.