I don't own a Sealyham but meet them around the shows, being in the same group as my dogs. They have a fairly typical, feisty terrier temperament, need a lot of grooming as they are one of the trimmed breeds and, similar to mine, are low to the ground so are mud collectors on walks.
You'll be fairly hard pressed to find a puppy in the UK though as they are on the KC At Risk Native Breeds list, same as my Skyes who had only 44 new puppy registrations last year( only 30 in 2011 of which seven were from my last litter). Sealyhams had slightly more at 63 last year. When you compare this with popular breeds,that can have registrations of thousand +, you can understand why most breeders of the rare vulnerable breeds have waiting lists, very long ones often going into two years or more.