Owning your own home

There aren't really any problems stemming from out of character in developments among 70's council houses. They aren't something that is considered something worth preserving in terms of consistency in the area. Provided the design of the building isn't something that would be considered an eyesore then there shouldn't be a problem on these grounds. Your main issue is on affecting other people's sunlight. Casting a shadow that significantly blocks another person's sunlight can cause a lot of issues in planning.

Awesome. Are you a surveyor/architect/...?