I have had air ride fitted to my MK5 for just over a year.
It was fitted by Luke and Co at Plush automotive.
Prices vary drastically depending on what you want,PLush aren't the cheapest, but they are the best in everything they do, and give great aftermarket help, like when a local garage cut through one of my air lines, Luke told me how to fix it, and when I went back to him he replaced it for me.
You can have manual adjustment, or digital, there is also remote control digital and e level, which automatically adjusts the ride height to what you set it at, and even when more people get in the car it adjusts it back up for you.
If you intend to fit it yourself you can save around £1600.
There is 2 way management, where you just move the front on one switch, and the back on another.
Or 4 way management, where each corner is adjusted independently (this is better as it prevents the air going out of bags on sharp corners)
There are a lot of companies that fit it, but as I wanted the best I paid slightly more than some charge.
Edition 38 has a lot of the traders, who can all offer advice and give recommendations.
Of course it doesn't handle as well as coils, but on day to day driving I find it fine, and have no problem with it, though it is better than the FK's I once had fitted.
Hope that answers some of your questions.