Whatever the case I would just keep quiet about it and not worry unless something cropped up. In normal planning once its been there 4 years they can't enforce anyway, not sure about listed buildings etc tho.
We are having ours done at the moment , similar area same blocks no manhole for roughly same price. Firm who did a neighbours 5 years ago. Was roughly mid quote of a few. Looking fwd to rain stopping so they can finish!
From your previous thread and photo it seems yours is the newer property and the wall us actually his garage? Is it a conversion?
http://www.diynot.com/forums/garden/metal-or-wood-gate-for-my-driveway.335455/
His/your buildings insurance. Surprised he allowed someone to build like that in the first place, is there info you are missing out? Are you sure his wall is the boundary line?
According to the dvla website you only need the vin to reclaim the original reg number. If you don't have a vin they can allocate a new one and allow you to get a new reg once you prove you have stamped the vin.
Sounds like a wind up thread but if its not, when you get your new boiler just remember you don't need to drain the system to change a radiator. Expensive bit of decorating .