So after several months of waiting (just over 6), I got a response from the VBA on both retaining walls.
Sadly it is no longer standard to issue 'built as' plans to neighbours anymore if a specific route is followed.
However, I have been completely vindicated in that the South retaining wall is now according to the plans - it would not have passed had I not been so persistent in getting it fixed - saved my neighbour the grief of having them come in to fix it after he had moved in and after the fence had been put in.
The North retaining wall has been found to not be according to design - as per my complaint. Though there is no imminent threat of collapse, it is not according to design and that could have serious ramifications down the line.
Problem is, neither that neighbour nor his builder would listen to me and now there is a fence and a concrete walkway on top of that retaining wall.
I'll be hanging on to that letter and should we ever sell, I'll pass it on to the next owner.
