Your power levels are fine, your modem logs mean nothing.
Have you alerted VirginMedia to your issue when you have no connection.
Do any of the lights change on the modem when your connection drops?
Do you have to reboot the modem to gain a connection?
Do you have to reboot your PC to gain a connection?
Do you get any errors, E.G a network cable is unplugged?
Have you tried to borrow a laptop/PC to test the theory that its not your PC, thus giving you something to present VM TSC with?
Are you using a router?
And if so have you tried with a direct connection?
Not helping us help you are you.
