I use
TPMS who are based in Redditch - not sure if they deliver in your area...
You could also have a look at
Berriewoods and
DAF which are other companies often given a mention.
Oh and yes you can feed carcasses just as they are - there's no need to mince them. I find the frozen ones often break into smaller pieces when I'm getting them out of the bag, but I suspect that slamming them onto the paving slabs will do that!!