If the coax has all been properly fitted, then yes the hub should work - try moving it and see. However, it is important that the coax socket that you remove the hub from (and any other spare VM coax ports) have proper termination caps on. If they don't you'll get radio signal noise ingress problems that will affect connection quality - hopefully there's a cap on the downstairs socket that you can swap? If there are uncapped live ports then you can stand on your rights and demand VM supply them (which is more easily said than done) or just buy a pack of F-type male terminator caps for around four quid.
If the move doesn't work, then VM only charge £25 for a non-fault call out. When the forum staff get round this post they can arrange that if still needed.
