What are the agreed terms of the deal?
Generally, the developer pays £1 on exchange of the option. Nothing more as the developer is taking a financial risk undertaking planning applications and incurring costs. If the developer gets planning then it will exercise the option and generally pay 10% deposit. The balance is paid on completion.
What option period is the developer looking for?
You may want to negotiate a revalue of the land on exercise of the option if you think the value will rise significantly over the option period.
I have on few occasions seen the developer pay more that £1 for the option but it is rare. It depends on the bargaining power of the parties and what you can negotiate, there is no rule of thumb or ball park figure, apart from £1 option fee. The developer generally pays the land owner's legal fees.
Any questions or queries?