I am willing to pay £5, but for that I expect a concession on the commercial use of my photos. Many zoos have a clause in the small print excluding commercial photographers or charging them a significant extra fee for working in the zoo. I haven't looked recently, but Blackpool's used to be particularly draconian even for amateurs - some of the photos in our Blackpool Gallery may breach the letter of this rule, but I'm sure we can claim it is 'fair use'.
Alan
Alan