Guys, thanks for the tips & experience. Guess I hijacked your thread jaybags but i hope it is broadly relevant to your original question. Ok, a bit of an update, I got some CRC cleaner for the air sensor. When I pulled the sensor off I noticed straight away that the resin on the end of the 'obvious' wire was coated in black dust (assuming it came from further down the inlet) but happy that it wasn't clearly road dust like in one of the examples in the "how to" thread on cleaning the air sensor. Sprayed it out a couple of times.
Had a closer look at the gland valve & had a bit of a poke around with a screwdriver..... Never believe it but I was able to clean out the crap sealant the snorkel installers used!!
Managed to clean it pretty thoroughly & heat up the gland with boiling water & hold it with a bulldog clip to try to get rid of the muntered lip thanks to the installers.
Got some of that sensor friendly Permatex RTV gasket sealant. Sealed the valve housing directly to the base of the airbox.
Leave it like that till tomorrow so it can cure & refit before work. I'll get my reader out & also see how the fuel consumption goes. All going well I hope to have salvaged my airbox & might not have to engage with the workshop responsible.... Or at least be able to put a different tone on it.