lol, I don't know how I missed it (lack of email notifications coming through) but I completely missed all the posts on page 2 and have just gone back and read them
For any newbies that read this at any point we might come across as being dicks as some of the responses are quite blunt and to the point like "buy a proper router". It obviously isn't what anyone wants to hear, especially when £££ is involved but believe it or not anybody who says it is doing you a huge favour by getting straight to the point and solving your problem for you pronto. If it was easily fixable then the op and many others wouldn't have spent so much time being mucked about by VM on the phone. If it was possible to change some settings on the router and especially wifi channels etc somebody would have suggested it. In this case the op described the symptoms of the fault and the steps he had taken to remedy it. We followed up by explaining the cause of the fault and the "only" way it can be fixed.
When there are known firmware issues which everyone is moaning about or connectivity issues VM's end then there is only one solution and it saves you so much hassle in the long run; buy your own router. I even went to the effort of making some sensible recommendations