This may be of their own doing, or it may be because their funder or insurer has asked told them they need to iron out any potential risks to the project. In such situations, the developer will want to check that their scheme will not cause you any loss of light, and if it is found that it will impact your property, they will want to rule out risk to their project, especially the risk of a potential injunction being pursued against them. If a loss of light to a certain level is found, they will normally wish to offer you some monetary compensation, to avoid you trying to pursue the injunction route.
As it is in the developers’ interest to eradicate such risks to their projects, it is normal for them to write to a neighbour to open up some dialogue. They may simply offer a sum of money as compensation. More often, they will first ask if their appointed surveyor can visit your property to do some internal measuring. After this, they will refine their computer model, and thereafter calculate results that show the light levels in your rooms as existing, and how they will be after their proposed development. Assuming the loss of light is of a certain level, then compensation may be offered.
The developers usually recognise that an offer of compensation to a neighbour may mean nothing to a layperson. As a neighbour, how do you know the developer’s surveyor has measured and modelled your property correctly? How do you know they have modelled the proposed development correctly? Is the compensation figure offered fair and reasonable? Normally, a neighbour will have no idea what level of compensation might be reasonable or not.
It is for this reason that developers usually write to neighbours and offer to pay the reasonable fees for you the neighbour, for a surveyor of your choice, so that your appointed surveyor can do the necessary checks on your behalf, and report to you independently. We can do this for you.