Dawes Super Galaxy - Tubes
Yes, the number most usually listed is 700x32, so anything with that in the range will be the right size. You can even get away with slightly bigger or smaller tubes in a pinch.

The ones you linked to should be fine, or try these from Schwalbe. Some people recommend Schwalbe for reliable tubes as well as tyres.

Note valves: It might matter whether you currently have Schrader (like a car tyre) or Presta valves. If you have presta, the Schrader tube valves might not fit through the hole in the rim. Probably simplest to get the same kind.