@Nkeshav as @jb66 rightly says above, VM's responsibility ends with 'does your Mum have a working internet connection?' and 'is it supplying over 50% of the rated download speed consistently?' If yes to both of those then basically you're on your own!
VM, as mentioned, do partner with a company which goes under the arresting name of 'Gadget Rescue' which they will push you towards, for the sum of only £5 extra per month for six months (I believe), plus a low, low one off setup fee of £20. Personally I have a suspicion that their skills consist of little more than 'turn it off and on again' and if that doesn't work then they are out of ideas!
Ok so you've done the port forwarding OK, the public IP address will have changed between Sky and VM so how do the cameras talk to the outside world? What sort of cameras are they, do they need a reboot to pick up the change of IP address?
