Garden boundary: is my neighbour being cheeky or should we cough up?

[ChristinaRussell]

We live in a semi, the other half of which was bought over three years ago but, due to a combination of the new owner's slightly OTT plans and a council planning dept from hell, has been unoccupied all that time and going quietly to seed. We have done the party wall agreement and are basically girding our loins for the horrendous, full-scale building work next door which will take months (and both DH & I work from home).

Currently the fence dividing our back gardens is in a state of extreme disintegration and has been for a few years. It needed replacing when he first bought next door (I'd come to an agreement re replacing it with the previous owner) but we held off because he was planning so much work. That part of our garden (and it's a town garden, so not huge, and this part is fully visible from our back windows) is looking really scruffy but we haven't been able to do anything because we've thought that at any time it's going to get trampled on by builders. His plan is to build a rear extension with a wall continuing on from that which will replace the fence.
The neighbour now says he's hoping to start next month. I'd emailed him today to tell him that we were going to go ahead and have our front garden landscaped because we couldn't wait any longer, and we really wanted to do some work to the back too. (By this I meant tidy up and re-do the planting, not build anything). He's just emailed me to say that he wants to build a brick wall along our front & back boundaries and did we want to contribute?! Now, through all the various meetings we've had with him and his surveyor (taking up OUR time for HIS sodding building work) he has NEVER mentioned our making a contribution. I don't know who has legal responsibility for the boundary - I need to dig out the deeds - but even if we do you'd think he'd waive that considering the inconvenience we've already suffered and will continue to suffer throughout the works?
Also, from getting quotes for our front garden I know that brick walls are very expensive and were we to replace the boundary at our own expense we would settle for fencing panels and/or timber.
So, would we be unreasonable to give him either a flat 'no', or offer to pay half the cost of a wooden fence? (By the way this was the arrangement we came to with the previous neighbour).

I think he has seized on the fact that we are doing our own work, completely over-estimated how much we are actually planning, and is trying to claw back some of the undoubtedly exorbitant cost of his own renovations. I think he owes us a f* of a load of goodwill and if he wants a fancy brick wall he should bloody well pay for it.

Sorry this is so long & convoluted - happy to give clarification if needed.

Collaborate, my neighbour replaced a fence with a wall. The fence was the marker of the boundary.

Collborate
But when a neighbour replaces a fence with a wall it is highly likely that the footings will cross the boundary
and legal action is pointless once the roots have been cut

@Movinghouseatlast A fence nearly always does mark boundary. It can do that and either straddle the boundary or butt up against it, whilst remaining on one side of the boundary.

Only the deeds can give a clue as to whether the boundary maker straddles or butts against the boundary. In the absence of any evidence at all the presumption is that it straddles the boundary.

@ListeningQuietly Not sure what you can about the roots? A neighbour who owns the boundary feature may do what they like with it, including removing it and replacing it. They have no automatic right to build a wall in its place without going through the procedure set out in the Party Wall Act. See para 25 on page 18 of this assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/523010/Party_Wall_etc__Act_1996_-_Explanatory_Booklet.pdf

On thing very clearly set out in the link I just posted is that any new wall must be at the expense of the builder. Again, see para 25 of the link.

@ChristinaRussell You need to make it clear to your neighbour that his proposed works fall under the Part Wall Act and you expect him to follow the procedure set out there.That means you can insist that they pay for a surveyor to advise and represent you.

@Collaborate the party wall agreement was done months ago, with a surveyor coming round - no mention of our contributing to anything.

He replied to my email basically agreeing to a wooden fence rather than a wall but still splitting the cost. I haven't got back to him really can't bothered right now but we think we might suggest that he does whatever he wants at the back (up to 6 ft in height) and he pays for it, but that we will sort out the front, as we can get it done within the landscaping we're planning & we'll have more control. To be honest I have so much to sort out in the front garden, as well as loads of decorating in the house that the back garden is the least of my priorities right now. It can't be done until his building work is finished anyway.

Tell them to start a new PWA process.