You can put pretty much any 26" tire on them, as long as it will fit between your brakes and doesn't rub your frame or fork anywhere.
The page on them at Alex ( http://www.alexrims.com/
) shows them to be about 25mm wide outside, and 20mm wide inside. Rather on the narrow end of things, as I noted in the other thread. It's something of an expensive upgrade, but if you want to run wider tires at lower pressures, it would be worth it to change the rims out to wider rims (at this level it might be cheaper to change out the entire wheels rather than have them laced with new rims). Tell your bike shop that you want "downhill"-width rims, and see whats the cheaper options you have.
This page (Raleigh USA) shows the Raleigh SC30 as being a comfort bike:
If yours is the same bike, then you may want to consider that knobby tires don't work so well for pavement riding. They squirm and lose a lot of energy when you pedal hard.