I had a similar problem and solved it cheaply. What i did was i called Virgin and after a bit of talking they offered to send the Super hub 3 free of charge to replace the Super hub 2. I then bought a power-line and connected the super hub 2 as an access point to the hub 3 (via the powerline) , in the area of the house where the WIFI signal was poor.
The superhub 2 does not have an easy setting to turn it into an access point , but following the tutorial below solves that and its not too hard:
http://community.virginmedia.com/t5/Networking-and-WiFi/Super-Hub-used-as-an-access-point/td-p/3074315
This however has nothing to do with the switching connections issue , it is just something i did personally that worked well.
To answer your actual question , if you bought a new router and spread them around the house all you would have to do is set the SSID (name of network) and the network password the same as the other router in the settings and you're devices should connect automatically to the router with the strongest signal automatically.