Don't want to question them? It's your photo, you hold the copyright and you say what it can and cannot be used for. Always, always know exactly what your photo(s) will be used for. If they just wanted to use it to hang up in their office, then £25 is reasonable. Now if they wanted to use it for a major ad running in newspapers & magazines worldwide, well you got shortchanged. I wouldn't have quoted less than $5,000US for that sort of usage/licensing. If you (and I don't me you Dan I mean everyone) plan to sell photos to major airlines/companies, please make sure you control the sale and not them. They are looking to you for usage not the other way around.