The advice if you absolutlely must change the location of your equipment is to always get Virgin in. The drawback is the expence (£99 for a non fault callout). If you can get away with leaving the box where it is & installing a long HDMI cable, you would save a lot of money.
Firstly, Virgin do not use standard cabling. They use specially made triple screened cable, as their coax forms part of the local network, and any radio interference or "noise" ingressing via sub standard cables or connectors will affect everyone in the street, & not just you. Secondly, your signal levels are balanced for the installation you have now. Any increase in the cable length has to be compensated for by an adjustment in the local street cabinet, or the performance of your equipment will go rapidly downhill.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile