Building regs part 1LB? Maximum area of glazing on extension

[Steveb21]

The area at the rear is an extension in progress.

Bi fold is 4.5m x 2.1m height
Window at rear garden is 900mm x 1.5m height

The line i have drawn in red represents a internal partition wall.
Floor space from red line to garden is approx 52m2

I am planning on removing the 2 sky windows on the left of the red line.
Either have 2 sky windows 2m x 1m height installed in landscape orientation (1 on each side of the rood),

or;
Have 4 sky light windows 2m x 1m installed in portrait orientation (2 on each side of the roof).

52m2 floor space
Am i correct in thinking that no more than 25% can be taken with glazing? If so that leaves me with 13m2
10.8m2 will be taken by by bi fold and rear window.
If i go for the 2 in landscape orientation at 2mx1m, that would add up to 4m2.
So total would be approx 14.8m2

If i opt for the 4 roof windows, it would total 18.8m2.

Advice required please!

By having the roof windows would i breach building regs part 1LB? (or should i work this out from the total size of the rear extension? - which is 99.5m2).

My BCO is on holiday so not had a chance to discuss with him yet.

 

[^woody^]

You can build it as a greenhouse if you know how to do the calculation