It may be Aerial Work if anyone is making money out of the flight, not necessarily the pilot. For example, if a PPL takes a professional photographer on a flight with the intention that the photographer does commercial work, it's Aerial Work even if the PPL doesn't get paid.
Given that what you are talking of is rather public, I'd get advice of the CAA first. See
http://www.nats-uk.ead-it.com/aip/cu...8_W_070_en.pdf - it has contact details for the CAA.