Air brick positioning

[Corjj]

I've done a bit of reading and ideally I know the air brick should be 1 course above the ground (75mm) and the DPC 2 courses (150mm), however in my case I'm a little more constrained. There are currently no airbricks on this end on the house as the previous owner's extension and conservatory has likely blocked them with solid floors.

I'm thinking about putting in either 1 or 2 air bricks just below the slate damp course, what are thoughts about this with regard to:

1. Proximity to drain, particularly if blocked.
2. whether say 25mm above patio level would be acceptable.
3. 1 or 2 air bricks? The front of the house has 2 airbricks about 9m away from this position (this bit being the furthest part to the rear of the house with suspended floor).

Blue markup on the photo is where the suspended floor ends and solid starts in the kitchen.

Thanks in advance

 

[^woody^]

Why are you fitting air bricks?

 

[Corjj]

There's one in the garage adjoining (extension) and with the plan is to convert it to habitable space I'm thinking if extended through ducts it will lose efficiency. There are also no airbricks this end of the house so the air space likely is becoming a bit stale.