I am not in the know as to the legalities of all this BUT,
Having not signed a contract with the previous owner then signing something kind of official with the new owner sounds like youve been caught by the short n curlies.

Youve said that you adore the job and cant afford to lose your job, It may be a bitter pill to swallow but surely its better to ride the waves for this short term for a long term advantage.

IE - Be skint for 3 weeks and keep your job OR kick up a stink and have no job, Harsh but could be true.