Over time various movies have gone off-copyright, whether because the original publishers have deliberately let them do so or it's happened because they've not renewed their copyright (the original copyright-holders could be long-since defunct so the copyright-renewal-letter went to a dead address...).
See
http://publicdomainmovies.net/ - lots of good 1940s/1950s sci-fi B-movies there! ! and some classic British stuff such as
http://publicdomainmovies.net/movie/...rst-of-the-few
What better to show on an old British TV?? Download the videos, and if you want a hard-copy burn them to DVD (but I'd not bother - replay from a memory-stick is much simpler).