Problems connecting to TV with iPad Mini

Hi there, please could someone help me with a problem I am having connecting my iPad Mini to my TV.

I have a lightning to HDMI cable which works fine connecting the iPad to the TV.

Many times I have connected it whilst playing a video/film, it has put the iPad into "TV Mode" where the iPad screen is not usable and the film plays the film in full screen at good quality on my TV (also getting rid of black lines around edges).

However, sometimes it doesn't do this and displays everything on the ipad screen in really bad quality whilst playing a film (as if it's streaming) because it's not on full screen mode.

I have no idea where I can activate the "TV mode" as it usually automatically does this when the HDMI cable is plugged into my iPad when the film is playing.

I am not using an Apple TV or a smart TV. Just a normal HD TV - So i cannot use Airplay etc. But it confuses me because sometimes the iPad goes into TV mode and sometimes it doesn't. And after the HDMI cable is unplugged and if I quit TV mode to use the screen again, once the cable is plugged in again - it won't go back into TV Mode?

I have tried for hours searching online for a solution that doesn't require Airplay or an Apple TV.

The Apple support forums are down and I cannot contact apple without having to pay them £25 just to email them a question!

I have been through all the settings on the iPad and TV as far as I am aware and cannot find anything about TV mode etc.

Also, both the HDMI cable and lightning to HDMI adaptor are quite new so they shouldn't be the problem.

Hopefully someone can help with this? Thanks! :-)