it's not like that ash. you can't ring up MOT testers asking if they can turn a blind eye to the emissions, it sounds like you're a VOSA govt employee doing the oldest trick in the book to catch them out. what generally happens is people build up a relationship with a garage or it's employees that they have known for some years and then little things like xenon kits with no headlight washers, decats, bald tyres, collapsed suspension components go unchecked on the MOT.
you need to find a friend that either works in the garage or speak to some of the local chavs that use the dodgy garages and get your introduction that way, if you just walk in off the street that is just bait.