As you are a self-employed photographer, your receipts from sale or use of your photographs would normally be receipts of your trade and so included in the normal way as part of your self-employed accounts.
BIM40051 - Receipts: general: whether trading income
In the scenario given, the question that needs to be asked is whether the payment received is on account of your trade as a photographer?
Whilst this has been called a compensation payment, it is not the name given to it that matters, but the actual nature of the payment. You have in effect engaged someone to negotiate payment for use of your photographs, albeit after they have been used. On this basis it may well just be classed as a normal trade receipt.
If you are actually entitled to the full amount of payment, then that should be included as you receipts and the costs of engaging the company would be allowable as a deduction (professional fees).
If the payments are correctly classed as compensation, then BIM40101 is relevant here.
BIM40101 - Specific receipts: compensation and damages: introduction
As BIM40105 states that the receipt(s) must represent profits of the trade/profession and that if the amount received is referable to trading operations, then it would normally be a trade receipt and included in your self-employed accounts as noted above.
BIM40105 - Specific receipts: compensation and damages: is it a trade receipt?