really you need a contract in place. wish you had said as i have these available, saves all the hassle, let me know if you need some help. OAT
Not so sure about that. I agree a contract would have made it much easier but the absence of one doesn't necessarily mean he's stuffed. A contract can be implied by the conduct of both parties, i.e. you have an email agreeing to pay you for the photograph, you have supplied the photgraph to them and they have then used it on their product. This effectively forms a contract between you.
Is the sum of money substantial?
You can issue a money claim through the HMRC website but you have to pay depending on the amount claimed. If it's worth doing I would suggest writing to them, enclosing a copy of the email, and saying that if they don't pay before a certain date you will issue a county court claim against them.
More info here
http://www.hmcourts-service.gov.uk/infoabout/claims/index.htm