Natives would most certainly not say "The weather in Britain changes really often."
We would say "The weather in Britain is unpredictable" or "The weather in Britain frequently changes" or "The weather in Britain changes frequently "
Formal language is infrequently used in the UK outside of royal or parliamentary speeches.
"The towns only cinema has closed down" or "The towns only cinema has shut down" would be used.
Formally (pretentiously) "The towns only cinema has ceased operating"
To be quite honest, it really just depends on the person that is speaking, because I have heard all of those statements been used before.
Most natives would often say something like-
"The weather in Britain changes really often."
As for the other one-
"The only cinema in town has closed down."
But really all of the statements in question are grammatically correct and able to be used in day to day conversations.