You may be presently surprised by the NowTV boxes.
Which ever road you go down be aware your going to need "Unlimited" broadband as it can eat easy +100 GB per month.
Just put one of these in the kitchen. £20 from Argos with 3 months entertainment pass. Good deals to be had for passes on ebay. Even you just get the box on it's own with no pass it's well worth it for a tenner. 4OD, iPlayer, 5 on demand, itvplayer and youtube are on there so loads of online content. You can also cast youtube to it from mobile devices.
Not HD though and you cant pause live channels.
If you have a media server with plex on you can put plex on the box and stream stuff from the server apparently