I had a 29 month Jersey heifer butchered. She was just under 200 kgs deadweight, and I got just under 120kgs meat back.
Our butcher liked his bullocks well under 350kgs deadweight, so I'd guess your Red Poll might be somewhere in the 250-300kgs deadweight range. You should get back a higher proportion of meat from a Red Poll than I did the Jersey, so perhaps 200kgs meat? Somewhere along those lines, anyway.
Do you know if the 40p/kg is on the deadweight figure, or on the meat actually returned to you? Would make a huge difference! I paid £300 total for the Jersey, including slaughter, but that included vac packing, labelling (with my labels) and packing in boxes (supplied by me, with freezer strips ditto) for my ciustomers.
The butcher made up 9 x 10kg boxes for me, each had a roasting joint, a pot roast joint, some grilling and some frying steaks, burgers, mince, stewing steak. Then there were 50 burgers on top (we had them at a special event) and a good few joints, quite a bit of mince and stewing steak left over for our own freezer.
All the joints were 1-2kgs, because that made it easier for the butcher to make up the boxes. You'll probably want some larger ones than that.