Too late now!!! (Score 1)

It is probably too late to do much about it now. You said that the "contract stated that the work that [you] had been carrying out off (and was planning to continue with) of [your] own back, and in [your] own time and was [your] own." How did you know? Did you consult a lawyer? Your employer did. All employment related contracts are one-side: They are written to protect the employer, and not the employee. If you thought your work was valuable, you should have taken the contract to an IP lawyer in the first place. It would have been cheap, and you would have saved yourself a lot of trouble (and money). However, if you came back with a redlined contract, you would probably not have gotten the job in the first place.