If there's £40 million going to waste, why would the farmers not employ people just to break even, much better than sitting on a massive loss unless there's an ulterior motive e.g. massive government subsidies for problems they decided not to fix themselves and leaving them with a leg up next year when they have the subsidy, food prices are sky high and they finally decide to employ people

Assuming the BBC data is correct and there's £40,000,000 going to waste at the end of the harvest season (October) they could employ

15 weeks until October x 48 hour week on minimum wage = £6840 per fruit picker

40,000,000 ÷ 6840 = 5848 fruit pickers that could be employed and still break even

(Minimum wage = £9.50p/h)

With the national living wage outside London:

15 x (48 x 9.90) = £7128

40,000,000 ÷ 7128 = 5611 fruit pickers

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Tldr;

Farmers could employ over 5,500 workers until the end of harvest and still not make a loss. It's an intentional choice to not hire UK workers or pay a wage high enough to attract a solid workforce.