Nwoody,
The Vueling website itself is actually the best info for the aircraft configs. When you run through a mock booking, it actually tells you straight away of the aircraft has 180/186/220 seats.
In terms of the base, the size of the current operation doesn't really give an indication of basing opportunities, and that applies to all airlines.
For example, blue air are bigger at Luton, but opened a Liverpool base. Norwegian were bigger at Manchester but opened an Edinburgh base and so on.