Just to close this off in case it is helpful if anyone is having the same problem.
If you have the hub 3 and see the following: Solid green wifi light, flashing green internet light (the two arrows in the middle), Solid green baselight (and therefore have no internet) you should insist on an engineer visit. The issue was further down the street in the connection box where the cable going to our house was faulty. The engineer was excellent and fixed the problem in about 30 minutes. As per other's comments, the hub 3 itself is still pretty poor and you should probably get some boosters if you arn't right next to it.
If you see the same lights as I did, book an engineer as no amount of resetting, turning on and off, checking the connections to your hub etc will fix it (despite the website's best attempt to stop you from calling). Unfortunately I wasted a week or so with no internet trying to go through the customer support system and should have been more insistent about requesting the engineer - I had to call 3 different times and was on hold for hours in total. The first time I called they said wait and see if it fixes itself and that they cant send an engineer, the second time I called I was told a virtual tech would call me back (they never bothered). The final time I called to cancel my service and they immediately sent an engineer.
Hope this helps anyone who has the same issue as I do - one thing I will say, be kind to the customer service when you eventually reach them! - it isn't their fault that virgin are too greedy to invest properly in customer service. Virgin have consciously made the decision to leave a small number of staff to take the brunt of everyone's frustrations just so a few greedy execs can line their pockets even more.