Tyres for these are not an issue. As long as you remember that's how they are spelled and they are readily available from any decent British cycle shop and on the Raleigh (UK) website. Just go on to eBay (UK) and you'll see several different types offered. The Raleigh branded ones are my favourites and being all black, period correct in every manner, and excellent quality. There are also IRC tyres in this size. I don't think the Schwalbe ones I put Sheldon Brown on to a few years ago are still made but I preferred the Raleighs anyway.
I don't recommend the Schwinn-sized tires... most are rubbish quality and the shape is totally wrong for a British club bike that these rims usually appeared on. They also ride like a truck. My 1949 Raleigh Clubman had a pair of these when I got it and when I switched to the Raleigh tyres, it was a revelation.
Peter Kohler
Washington DC USA