It is not the responsibility of your local planning department to check that you’re building within your legal boundary. They view boundary disputes as a private matter between neighbours. They are only concerned with the impact your property could have on your neighbours. For example their privacy, access to light and on the structural stability of their house.
It’s up to you to make sure that your proposed building doesn’t cross or overhang your legal boundary. Just because you have
planning permission for a certain area, it may not be yours to legally build on. Planning consent will not protect you from a dispute brought on by a neighbour. It could halt your build and be extremely expensive.
Planning applications can be another source of boundary confusion. The borderlines of the area with consent are drawn in red on the site plan. This is based on Ordnance Survey maps at 1:2500 or 1:1250 scale. This thick line along with the scale of the plan could be misleading about where the boundaries are. If the site has detailed planning permission, you may benefit from a 1:500 or 1:200 scale layout diagram. Which could offer a clearer picture. Comparing all other boundary drawings with the original deeds, is still the best way to be certain.