With observation of international agreements on copyright conventions- the UK, along with U. S., Canada and other Commonwealth countries and I think most if not all members of the EU, is signatory to the Berne Convention, whose terms are carved in stone by the WTO's TRIPS agreements.
Article 7 provides a general minimum term of protection of the life of the author plus 50 years with variations for particular types of copyright work. For musical works, the period is life of the author plus 70 years (1995 amendment) as Jack Campin posted. As Nerd posted, in the US this is extended to 95 years.
I remember the Olympics in Salt Lake City; musicians at the games could not play "Waltzing Matilda" without payment although it was free of restriction in Australia and UK.

As most commentaries suggest, copyright regulations are a mine field; unless one is a soliciter schooled in the regulations, beware!

The regulations of the Berne Convention are incorporated into the World Trade Organization's TRIPS agreement (1995), thus giving the Berne Convention effectively near-global application - as a minimum.

Taking the simple-minded approach, if a UK composer kicked the bucket in 1938, I guess his music is pd there, but if he also obtained U. S. copyright (as many do through their publishers), then 2063 is the magic date in the U. S.
Dunno the regulations in the various EU countries.

Canada follows the Berne and Universal Copyright Conventions. With the U. S. on its border, there are possibilities for problems.

For certain, only the hog gets eaten on New Years day.