So after thinking first Sky were at fault for my problem and then Virgin Media it seems its a communication problem between the VM router and Sky Q minis.
Up until a few weeks ago it Sky Q had worked great. Sky Silver box in the living room, mini next door in the kitchen, booster on the 1st floor and 2nd mini on 2nd floor connected to said booster.
Couple of weeks ago the 2nd mini kept losing connection. After a call to Sky it seemed that the booster may have dropped off the wifi and the 2nd mini was trying to connect to the Silver box. Now after a total reset the minis wont connect at all to the router as it wont assign IP addresses.
Virgin are saying it must be a Sky software issue as their routers wouldnt just not assign an IP address.
Any ideas what to do next other than scrap Sky which i dont want to do!