206 jock,
The sites you mention were created by the MK Development Corporation - not sure if that organisation still exists - try MK council. There is one right next to Jct 14 as you say. I thought that the phone number for PP was in Pooleys or the Sitefinder. I also looked in Griffin Helicopters - the site is there but no contact details.
OS GR SP884412 OS Map 198
Some of them are in congested areas. You will have to judge how the Jct 14 site looks