The ARP has nothing todo with the rwy coordinates. This is a own point but completly independent from the runways.
It’s a luck, that the ARP at EGCC lies on the runway 05L/23R - if this is really the mid point, I don’t know but I wouldn’t expect it even when it looks so on the airport chart.
As I wrote before, the runway coordinates are the center threshold of the specific runway, the markers are inside it.
Cheers
Richard
PS: I have checked the EGCC runway and ARP coordinates now against the UK AIP and the values are correct. So I’m not sure what you want report here, where do you see an issue here?