What about all the British people who live in Europe. Most of them don't integrate or adapt. They have their British pubs and shops, bowling greens, schools, retirement homes, and theatres. They run Royal British clubs, Scots clubs, Irish and Welsh clubs holding big celebrations on their national days. They have a wide range of other English speaking clubs. They have their own churches with services in English. They use the local health services. They print their own newspapers, have websites especially for them in English and radio programmes and watch British tv on the Internet. The don't learn the language and proudly say the locals speak English
Isn't that what you complain about immigrants doing although we definitely don't speak their language.
Also if we leave Europe a great number of the elderly ex pats will come back to be cared for if they can no longer use the local health services making a bigger strain on our NHS and so we will have to employ more immigrants to look after them. Some won't be able to buy a house so we will have to provide local authority sheltered housing,
One reason to stay in Europe