Pretty much the standard basic ‘workhorse ‘soldering iron, for stained glass, seems to be the Weller 100 watt electric thermostatic iron, readily available in the UK. I would highly recommend it.
In order to get a decent raised solder bead for copper foil work, an iron that can consistently provide the required amount of heat is needed. A thermostatic iron maintains the temperature and this particular iron does that very well. In addition, different tips are available that allow the iron to perform at different temperatures to meet different requirements.
A much cheaper soldering iron (non-thermostatic) is also available but it is only really useful for spot joints, as it is very difficult, if not impossible, to get a decent bead for stained glass work with this type of iron and then having to buy one of the expensive irons later on makes it a false economy. Better to save up and go straight for the thermostatic one.
Less frequently used, I would also recommend the Weller 200 watt, for bigger work where more heat is needed – such as working with wide lead and in complex joint work.
Whatever iron is selected however, a good stand is really important. Basic stands that tend to come with irons are usually a piece of aluminium that is then bent into shape. A purpose-built stand has a heavy base, so is more difficult to displace and it usually offers a more convenient angle to hold the iron at readiness and has a space for a natural sponge (to help clean the soldering iron tip).