Subtitles have been developed to improve access to television for people who are deaf or hard of hearing.
To get subtitles on analogue TV you need a set that has teletext so that you can access Ceefax on BBC One and BBC Two, and Teletext on ITV1, Channel 4 and (if you can receive it) Five. Subtitles are on page 888 on all the channels. Some remote controls have a button that goes direct to subtitles.
It is possible to record teletext subtitles with some video recorders, but this is becoming more difficult as new methods of recording replace video. Recording subtitles from digital TV is much easier.