Probably not. In general you can only deduct expenses you actually pay, and your own labor is not an expense. You could hire someone else to do the work and then the amounts you pay them would be deductible expenses. Your suggestion of paying yourself to do the work probably won't help you, as then you have additional personal income to pay tax on. Depending on how your business is structured, it may not even matter how much the business pays you, since you'll probably pay similar amounts of tax on business profit as personal income. If anything, usually it's more beneficial for the business to pay you less rather than more. And if it were beneficial for the business to pay you more, then as the owner you could do that regardless of if you work these extra hours or not.
Disclaimer: I'm not familiar with UK tax laws, and this answer is relevant for the US. I suspect the concepts are very similar though. (And skimming through the UK business expenses rules confirms my suspicion.) In general, if you could deduct your personal time from business expenses, suddenly every owner would be claiming they work 100 hour weeks... ;) By the way, the same reasoning applies for why you also can't deduct time you spend when you do free consulting for non-profits.