A little update 2 weeks after they finished the work. It was also the first significant rain/snow we had so the first chance to check the drainage. The rainfall wasn't as significant as some of the downpours we had towards the end of last year but nonetheless there doesn't appear to be any areas of flooding both on the patio and the grass. The grass is nice and green, I've been watering it on the days where it hasn't been raining. I can see the roots slowly starting to come through the turf which I hope will start to work their way in to the soil.
The aco drains has water in it so it seems to be doing it's job. The water isn't exactly flowing away like a torrent but at the same time it isn't backing up and flooding. Initial impressions are encouraging.
I don't feel the need to get the squeegees out to move the water away from the air bricks so I'd say that's a good outcome.