Firstly, the vent shown in the photo would allow water to get under your floor. It should be higher than this.
This vent has weed fabric at the bottom which would allow excess of water to go underneath instead of into foundation, there is an extra bit coming out of it which can't be seen on picture but it is higher then bottom of this plastic, so any water would go down under the foundation, also floor level in house is between yellow and red brick.
Secondly the gap in the blockwork should have been made good around the pipe.
This vent shouldn't be even in that place, below is a sewer pipe and that is why they left that gap there between the blocks, vent apparently should be 100mm to the left or right - it was left there as it was easy to push in an end which suppose to be connected to the membrane.
Thirdly, if you have or need a gas membrane (only required if you home is built on or new a rubbish tip or there is a presence of Radon Gas, then it should have been inspected by the warranty provider and signed off for building regulations too.
I requested Radon report online and house is build in Radon Free area so this is good, I don't also have a knowledge about this place being a rubbish tip before.
What is the sleeved copper pipe in the photo for?
haha, it is a chisel which I used to dig it out.
I'm perfectly happy to leave it as it is if doesn't require connection (another 3 are connected correctly). I wasn't sure if this was a building requirement to put them in all new houses, but it looks like builder was putting them as a precaution then.
Thanks !