I phoned a butcher in Lincolnshire where my mum gets her meat. This is what he said:
Cow - Lincolnshire Red, a native bread (75% native), higher fat, slightly smaller, late maturing, completely grass fed
Weight of one side - half a cow is 150kg or 330lb
Cost £750 or £5 per kg; beef prices are stable and unlikely to change
There are three qualities of meat in a cow:
top and silverside - 30%
rump, sirloin, fillet, ribeye - 30%
brisket - 40%
And any of these can be cut into different products eg mince or stewing beef, steaks or roasting joints.
He would need to know the numbers of people and how each person wants their proportion cut.