Neighbours & party wall agreement

[BusyCee]

Our back door is 1.8m above the garden (house is on a hill). A couple of years ago we built decking from the back door with steps down the to the garden. Earlier this year the neighbours complained about our decking to the planning dept, and retrospective planning consent was declined (as we had expected). We saw this as an opportunity to improve the living space and access to the garden, so proposed an extension. The neighbours objected again - but we recently received planning consent. As we'll be building within 3m of the neighbours we need a party wall agreement. I heard today that they have decided to appoint their own party wall surveyor, rather than allowing ours (who is an experienced architect, who also lives on our road) to work on their behalf. Naturally, and quite legally, we will bear the cost of this.

Throughout this, our neighbours, who we had previously been on very cordial terms with, haven't uttered a word to us. They have been actively avoiding us. We've taken their cue, and haven't pressed anything - they clearly don't want to engage in a discussion - although have remained cheery and chatty when we see them.

My question is; has anyone experienced a party wall dispute like this? I'm wary that they are intending to make as much difficulty and disruption to our building as possible, and it would be useful to be forearmed. I'm sorry they aren't happy with our plans, but I don't believe them to be disruptive to their property (and clearly neither does the planning department).

You say they haven't uttered a word but then say they are cheery and chatty.

They obviously do not like the plans submitted and don't want to engage with you about that but are happy to be cordial on a day to day basis. At least that is the case and they aren't being horrible.

I assume they believe the proposed extension will detract from their property in some way either in value or outlook etc. It was their right to object, to ask for their own surveyor etc and I assume they have taken the view that it was up to the authority to decide (which was in your favour) and that their surveyor will act in their interests to ensure their property is not damaged in any way.

I suspect once the extension is up they'll either get used to it or they'll decide to extend or move themselves.

At least they aren't being really awful even if you feel a bit uncomfortable.

This isn’t a party wall dispute (yet) - it is absolutely reasonable to elect to have your own surveyor; why would you not choose to have someone looking out for your own interests rather than someone who is supposedly impartial but in reality is appointed by the building owner?
If your party wall person is as good as you say you have nothing to fear - they are quite used to working alongside and reaching fair and equitable agreements if there are any disputes. They cannot stop you bUilding once you have PP - it is more agreeing the terms and detail as it affects the neighbour.