A wayleave is the right to have a piece of apparatus within land ownership other than your own with a series of caveats covering access for maintenance purposes only.
This would not cover for example a new borehole only the maintenance of the pipe and pump. Anything in a new location would not be covered. I would suggest a land agent in the first stage at the other guys cost.
Either way you will be left with a burden that would be passed on within your deeds.
All of the above should be the focus, with a clause where by if the supply is used for any other property a further wayleave payment would be paid, this would be the norm, should you agree to it
All of the above is valid in Scotland, if you need any further help PM me