I think you are over looking something rather obviosu in the exempt regs
pico wrote:Does a grant with conditions (permitted development) override one's right under a different part of legislation (exempted development) ?
No it doesn't over-ride the permission. But that's not important.
Take the obvious example of building a house, as per the grant but with a 40 sq.m extension.
Many sugguest they can do this as its extension is exempt. But they are wrong.
If you check the exemption regs, its is only exempt to build an extension to a dwelling, therefore it must first be construicted. A slab and half built walls aren't a dwelling. You can of course be clever about it and get the roof on and leave the internal finishing until the extension is built. or get all the foundations in at once (sub ground work won't need planning imo)
The same applies to an exempt shed or garage conversion.
Those are the two that I am familar with regarding this issue, the "curtiledge of a house" applies to almost all the first exemptions. The ones it doesn't apply to would be painting and plasterign a wall, but its not an issue here as obvious they have to be built first.
The change of use exemptions doen't really have an issue here imo.
A whole load of exemptins are for state bodies, so not an issue here either.
Blustar, is your example not covered by the above.
I can think of some contrived situations, where a 30sqm is grant and a 40 could be built under exemption. But I don't think there is merit is getting into those example.