NowTV probably one of the better ones. It’s IPTV.
Needs (wireless) internet to work.
Can work on SmartTVs That may have the app pre-installed. But if not, you can buy a stick so that it will work on any TV with an HDMI socket.
NowTV Stick
The basic stick costs less than £25. Usually includes a month or two of Sky pay TV for free. E.g. Entertainment pack is about £8 per month.
If you don’t subscribe to anything you can still use the stick to access the apps for BBC, ITV, Channel 4 & C5 and watch live TV online that way, plus all the advantages of iPlayer downloads.
You still need a TV licence if watching it live, but no TV aerial. Just internet connection.