Ok thanks. Sorry - it's not good news I'm afraid. The landlord is entitled to serve the notices to quit and they are giving the correct common law notice period. As a non - business user, you have no statutory protection. I suggest all you can do is seek to get the price down. Sorry!
Possibly, but it will depend on the exact termx of his agreement. If it prohibits uses other than as a garden, he's in breach and can't use business use as a means to claim a protected business tenancy.
Sorry, but I think you've not got any legal options, only practical ones such as trying to negotiate a better deal.
No, sorry. Unless the agreements say so, these things were done at your own risk. I am sorry, but this is the legal position.