Bungalow under PD?

Q: I have found a plot of land, large part of a garden with access, where there is already a house on the site, with space for another one or possibly more. The area is XXXXXXXXX, residential, with mostly 2-4 bed terraced or semi-detached houses. Council have already indicated that they are likely to grant access from the carpark belonging to their development next door. They also suggested that the owner could build a bungalow under permitted development – would this be possible? I doubt that it would make sense financially. The houses in the area are mostly 2 storeys. Do you think that in the area which is approx.. 10x25m you could fit in more 3-4 houses like the council ones as opposed to just a 3-4 bed, similar in footage to what is already there? To make things more interesting, there might be a possibility of acquiring the garden to the right of the one highlighted below, at a later stage. It is not available at present though.

A: Lots of questions in there so lets take things one step at a time.

Access from the car park to the land in question would be essential but i doubt that the LPA would grant this without a substantial charge. This needs to be factored into the financial models for the application site.

There are no permitted development allowances for the creation of a bungalow under permitted development so I am wondering if either the Council or the Vendor are giving the correct advice here. It feels like an oversimplified statement anyway and as such I would want to see the correspondence from the council that confirms this otherwise mythical PD allowance.

The site is in a backland location and the National Design Guide and Urban Design Compendium both advocate dropping at least 1/2 a storey out of overall building height in order to have an appropriate relationship with its surroundings. This is especially relevant as the site is significantly overlooked at close range from two key elevations.

250M2 is not sufficient for 3-4 houses and the plots are in no way comparable. For terraced you would need a plot of at least 1600M2 and that would be a push here. To do this you would need to acquire a substantial number of gardens (not just the next one along) in order to make this work properly.