As advised by other posters, you need to take qualified legal opinion and look into this very carefully.
Something very similar happened to my cousin by marriage (some years ago) but he had all his ducks in line. My cousin is an accountant and tends to see the world in pounds and pence and be quick to spot a potential business opportunity.
Pushy new neighbour tells Clive (cousin) that he is having an extension built and that some of the scaffolding posts “will be going” in his (Clive’s) garden. Now Clive and his wife are very keen gardeners and have spent much time and money on designing their garden and employing a professional gardener.
He was taken aback by this arrogant attitude from a new bug in the area, but politely asked pushy to produce the plans and show where the “proposed” scaffolding poles were to go. Neighbor produces plans and they discuss the length of the build which was projected at 3 months. Unfortunately the proposed location of the scaffolding coincided with an area where there is a water feature, a seating area and nicely landscaped flower beds.
Clive tells neighbour that he will discuss the matter with his solicitor and get back to him with an estimate for “renting part of his garden” for the build plus other costs. Pushy is open mouthed at having a solicitor involved, and insists its simply a matter of “bunging a few quid” to account for a few holes in the ground. Surely you don’t need all this with a neighbour!
Clive now delivers his classic speech of which this is a summary:-
“Lets leave this neighbour business on one side. Im a business man and you’ve come to me with a business proposal so I mean to handle this is a proper and legal manner. This build is not for my benefit and I intend to protect the interests of myself and my family. As well as the cost of renting part of my land there are other considerations, such as:
This will spoil our use of the garden for the entire summer
It will restrict our privacy
The scaffolding poles may constitute a H&S danger to my grandchildren when they visit
My time and that of my wife are going to be involved in arranging access, liaising with tradespeople, etc
Damage to and restitution of my garden to its former condition
etc
I will need to ensure that your workpeople are a legitimate company, properly qualified to carry out the work with care and skill and fully insured to cover any potential damage to my property. That’s why I will be involving my solicitor, and any other required professional, for whose services you will be asked to pay out of your contingency fund for the build.
As I promised, Ill speak with him and get back to you.”
Clive gets back to pushy after an interval with a proposed estimate costing. However no more is ever heard of the build. Pushy eventually re-submits his plans and switches the extension to the other side of the property. However he meets with a similar response, because Clive has already pre-warned the other neighbour. Subsequently the property is put back on the market.