For linseed you are looking at c£100/ac in seed, fert and spray costs (roughly £30 each for seed, fert and spray, plus a contingency). Add £100/ac for "rent". 2 fert passes, scratch & till establishment or DD into subsoiled land, 3 or 4 sprays and combine. Budget on 0.8t/ac. How you account for your SFP is up to you, either way the profit element is nearly lacking.
Spring beans really need ploughing for in my view, and drilling properly. But ironically, costs about the same on a 5yr average to grow as linseed. Budget for double the yield at half the price and a later harvest. Also poorer weed control with no simazine.
Peas technically best payer but highest risk of disaster. Also want better ground that beans or linseed. Peas will also increase your slugs.
All spring sown combinables are poor payers it would seem. Again, depends on your attitude to paying yourself a real rent, wear and tear or paid-for kit, contractors costs, and enjoyment for working for £20 an acre or so. I think it is getting marginal at £287/ha margin to grow any crop - better off with a winter bean / vetch / mustard green manure and getting the land fit for drilling wheat in September again.
Take the dough and stay real jiggy.
Uh-huh.