I would be surprised if anything that's 50% Castlemilk Moorit would be ready to kill in 5-6 months.
It's unusual to put a ewe to a tup that's a lot smaller than herself... I'm not sure a Texel ewe would even let a Castlemilk Moorit tup mount her. If you want to try commercials it'd maybe be best to be Dutch Texel or Beltex - much smaller than regular Texels, and so muscley that hopefully the offpring would have some value as meat lambs. Or what about Southdown, the offspring of that cross would be useful for their fleece as well as for their carcase. Or Lleyns - the females would be nice breeders to retain, the males would make nice hogget the following year. (Sorry, I really don't think any Castlemilk first cross will finish in one season.)
You could try Jacobs, Southdowns or Shetlands, and sell the offspring in the store in the summer - other smallholders may like to have them for lawn-mowing and a fleece and super-tasty lamb / hogget next year. And Shetland x Castlemilks make lovely ewes, you could either retain them in the flock or sell them as breeders to other smallholders and small farmers.
You could try marketing purebred Castlemilk Moorit wether lambs as stores for crafty smallholders who would take a fleece off them the following year and then enjoy some lovely rare breed hogget meat.
Not being much help, I suspect. Sorry!