Sorry, should of made it clear that when I said "consider these points" it was directed at the OP and not you, my badConsider these points:
I have not seen the original post with the letter, but if you go through the posts the situation changes from no contract or agreement ever existing, to the agreement being detailed on the team forum and having been updated at a later date.
Contract law in England requires:
An offer
Unconditional acceptance (this allows for counter offer & negotiation)
The existence of the agreement on the team forum indicates these 2 elements existed (even if subsequent individuals in the team hadn't been party to the original agreement they still take on responsibilties as appropriate by joining the team)
Consideration Everyone must get something out of it. The sponsor receives promotion, the team gets the sponsorship benefits
Terms Not everything in a contract or agreement is considered an enforceable term. This could have bearing on the current situation
Termination A way out of the contract. This definately has a bearing on the current situation
Damages This appears to be the crux of the matter, and the sponsor is seeking them
Intent There must be an intent that the contract or agreement is enforceable. This possibly has a bearing on the current situation as the original poster does not seem to feel he was in a contract (or that he has the impression that because he was told by another individual that the contract/agreement has been terminated or he was able to terminate
But yes after looking back the whole situation is a bit vague and all over the place.