The coax cable is something VM will resolve with a "non-fault" call out for £25. Might sound excessive. be assured that the cables you'll find readily advertised as "Virgin Media compatible" are not VM approved or tested for use on cable internet, and frequently are not of an adequate quality for the very demanding requirements of cable. I won't bore you with the technicalities, but cable internet requires very high quality cable, properly made up, and just because it looks like bog standard satellite cable, it isn't. Moreover, on a longer run you risk the signal power levels dropping off, that would need checking and adjusting by a technician.
I don't think VM will be able to do anything other than provide a standard power cable (you can of course ask). If the answer is no then options are as follows. If you're using a "wall wart" power supply, then you'll have to use a mains extension lead which can be a bit clunky, or you can buy 12V DC extension leads to go between hub and PSU. The trick here is to know what size connector the DC plug into the hub is, and as I don't have a Hub 4 I can't tell you. 5.5mm jacks (plugs) are the most common, but they can have 2.1 or 2.5mm pins, and the wrong size will not work. If you've got a micrometer, you know what to do, if you don't then you may have to hope some kind forum member who does know can tell you.
If your hub has a "power brick" power supply, that'll normally have a separate mains lead ending in a figure of 8 connector. The technical name for that is an IEC C7 connector, and if you search for something like long IEC C7 cable, then you'll find plenty offered in a range of different lengths, some with a UK mains plug, others unterminated and you'll need to fit your own.
