Ongoing broadband connection issues

Over the last two months I've had various issues with an unstable broadband service with outages ranging from a few minutes to days. 

I've had 4 engineers out in that time frame that have tried various solutions including a new router hub, changing a cable splitter and testing all connections amongst other things. All have left with the issue "fixed" but it only lasts a fews days before the connection goes unstable again.

The latest manifestation of the problem is that over the last few days connection goes down pretty much bang on 1730-1800 and doesn't come back until midnight-0100, then running fine until the evening and repeat.

Frustrating as need internet for work, son's school homework and equally important for evening relaxation and ability to use streaming services we pay for, not too mention virgin now failing to provide a suitable service with no solution or recompense.

I should add the previous 2-3 years at the address have been largely trouble free barring wider network issues.

Any suggestions? Or is it time to look for alternative suppliers in the area?

Cheers