FaceTime not working after certain times

Hi there guys and girls. This a strange little question regarding FaceTime and FaceTime Audio.

Generally my calls to other apple users are perfect, however after a specific time of day the calls drop out every few minutes and even iMessage texts are delayed.

It mainly happens when I'm calling someone in USA as I'm living in the UK.

So usually from 1am to 5am the issues crops up.

I have done the usual, soft reset and hard reset. I've tested it over wifi and LTE connections.

So I'm going to put it down to Apple server issues, which are pretty vague when you go to the status checker to see what's up.

Have any of you come across any issues like this?