Voxi would be a good contender.
£20 for 45gb of data, along with endless data for video services so Netflix, amazon Prime, TV player and my 5, along with endless social media on Facebook twitter WhatsApp etc.
As well as standard unlimited calls, texts and picture messages, plus WiFi calling and 4g Calling included if you wanted to use it in a handset too.
Depends where you'll be streaming your movies from. Tethering is also included for the endless data.
Smarty generally £16pm if you look about for unlimited data.