Patio and Damp Proof Course advice

[JamesWNoClue]

Hello, I have recently moved into a Victorian terrace with a small back yard which has a small patio area and a slightly larger pebble-floored area. The patio area is clearly sloping towards the house and has a drain to deal with the runoff.

I would like to replace the pebbled area with patio and am trying to find out whether I should keep a border of pebbles or if I would be better putting a drain channel flush to the wall, as already exists on the existing patio section. On removal of the pebbles, I believe the distance between the DPC and the floor is 150mm. The drainage channel I am looking at is 50mm so the distance with the drainage channel would therefore be 100mm, which I understand is below the recommended, but surely this would still be better than the existing pebbles which is barely 50mm below the DPC? Or am I mistaken?

First time doing anything like this and so am wanting to get it as right as possible and open to anyone more knowledgeable to give any advice!

Pictures below

 

[Wayners]

Not my area of knowledge however.
I think your better off with drain.
Gravel works around houses keeping water away from masonry but you can put a drain in no problem , as you have pipe to take away.

 

[Garyivy]

I’d be comfortable with 100mm, I think the drain helps run off water as you say but the min height is to deal with bouncing rain I think