Any particular reason for a Lleyn? You can use most of the larger tups for crossing Shetlands - so if you don't want to keep a tup all year round just buy a Texel, or Cheviot tup lamb let him do the business and sell just before Xmas.... (depending on the number of ewes you have of course and you may have to feed him during his stay with you). Unless there is a Lleyn breeder near you (you could check on their website) Lleyns are probaby dearer...