as a general rule you cannot supply your own cable - start from there and you will not go far wrong
you say you need 3 cables - one for the hub that but i know - the other 2 for TV boxes i assume - i am not sure on those and i think it can depend which tv box you have - some need a BB connection so assuming they do that explains the 3 cables
to have 3 BB inputs you need to join the 3 cable back to a common input from or in the omnibox [the external box on the outside wall] so there may be a 3 way splitter in there or it could be internal - ir you could start with a 2 way splitter and then split one of those inputs again with a second 2 way splitter - its all down to the layout of the house or the placement of the hub and tv boxes
you can certainly pull the VM cavle with your existing aerial cable into the loft or wherever - if the end connector does not allow that cut it off and the tech would fit another one
where the techs will go - in the loft - under floors is all down to the tech on the day - i was talking to one the other week who said he was happy to do that but stressed that was his choice not VM policy
how did you actually arrange to get the cable - it may have come via an AFM but customers cannot normally contact them so who set it up in the first place
how long is the cable thats been sent - is it long enough for all 3 cables you need - if it is cut it and dont worry about the ends - gat all 3 input ends back to a common point where the input will come in from outside - they would then just add a 3 way splitter and all cables would be good
if you have not already it sounds like you need a site survey - VM [here] may be able to arrange that
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Tony.