We have run a small maize in the grounds of a stately

Hi,
We have run a small maize in the grounds of a stately home for the last 8 years. We purchased it for £4.500 from the lady who originally set it up. The Estate Manager was aware that we had paid her this money yet despite many promises, never issued us with a lease, it was all done via a verbal agreement. The Estate plant the maize crop for us and in return we give them 20p for every person who visits. We have now built up the business and branded the name, spent a lot of money on advertising and getting ourselves known and they have now told us that they are taking over the running of the maize in-house to take effect immediately! They have offered us no explanation or remuneration and have advised us that they do not want our log cabin and we should remove it from their land.
Surely, this is wrong and unethical! Do we have a legally binding contract as we have fulfilled and completed the contract for the last 8 years and have always paid any money owing to the Estate at the end of each season.
I look forward to your response
Yours sincerely
Andrea *********