3rd party power adapter causing screen glitches?
It's almost certainly the fact you're using the 3rd party UK plug power adapter (although it's not clear to me how you're doing this).

Regardless, as a simple test to confirm, all you need to do is plug your iPad into a USB port (e.g. on your Mac/PC) using the same cable. If the problem doesn't repeat itself, you have your answer. 

If it does still occur, you know then that's it's likely the cable or iPad itself. You could then double-check there's nothing inside the Lighting port of your iPad causing interference/conductivity issues. If there's nothing obvious, retest by using another cable.