Cheers for that. There are some pdfs on there that give some good details but it's hard to know if the development is going to be particularly intrusive.
So far as impact of developments in general within the World Heritage Site is concerned the local planning committees haven't a very impressive record so as a rule of thumb it might be best for the public to take more note of what some of the consultee bodies say about all such issues - the World Heritage Site Officer, the County Archaeo and EH for instance. There are a number of far more potentially controversial issues coming up where that's likely to be very important.
I think you are not only right but hit a particularly worrying nail on the head.