Mixed cattle and sheep would give better returns.
Output per acre of both increases under mixed regime.
Also, in a year when sheep aren't doing so well then perhaps the cattle will make up for it, and vice versa.
Shrekfeet's figures are pretty fanciful.
Gross margin per ewe is likely to be in region of £27. That's about 1000 quid return from 40 ewes, and that's before overheads like rent, morgage, overdraft, labour etc.
Obviously depends a lot on breed, management and marketing strategy. You can do very much better than that, but best not to make the budget too optimistic.