There are a few on here now with air, your looking at a starting price of 2.5k, plus £700/1000 for fitting, not many have installed themselves apart from my self, if anyone has fitted it themselves then good on you
Most people take it for mot if it passes it passes if it doesn't they get it fixed, there are thousands of members on here past and present who know nothing about how to fix there car, so I wouldn't have an issue about mot advisories,