I’ve just got myself a new kindle fire, mostly for box set’s and movies though I will be using spotify too. Looking for some over ear closed back headphones, from Amazon would help and sub £50. Should I be looking for something specifically for films?

£50 will get you some AKG Y50s. They are on ear not over ear so there is some sound leakage… I’ve got the Bluetooth version and I’m impressed.
They get pretty good reviews:
What Hi-Fi

For home use I have some over ear Sennheisers. They don’t leak sound at all.. The nearest equivalent now would be the sennheiser HD 429S, they’re within budget too….

Audio-Technica M20Xs. The Y50s maybe ok for films but they’re garbage for music.

I have a pair of AKG K450’s and they are very good.
On ear but little sound leakage and very comfortable. They fold up and have a single replaceable cable so you don’t trash the headphones when the cable dies.

Highly recommended and bang on budget – I use them rather than over ear ones these days