You will have to lose your playlists. Some of your music might well not be available in the UK anyway.
In the legal documents: Legal - Apple Media Services - Apple section H you will find, "When your Paid Subscription to any Service or Content ends, you will lose access to any functionality or Content of that Service that requires a Paid Subscription."
For purchased items (not Apple Music offline versions) "Redownload your apps, music, movies, TV shows, and books on any devices that you might use to play or read them in the future. Some types of content might not be available in your new country or region. (Learn what types of content and services are available in your new country or region. - https://support.apple.com/HT204411 )"
As long as you have a copy (preferably on a computer) you can sync it to any future iPhones or iDevices you have.