Poor or non existent rail links to UK airports

I read the article lamenting the poor rail links to UK airports
and thought of two main airports in central Scotland. Neither Edinburgh or Glasgow airport has rail link. EARL, the Edinburgh Airport Link has been discussed for years. A recent report now suggests that if the EARL is built there may not be need for a Glasgow Airport Link.

At present you have to take a bus from Edinburgh city centre out to the airport. For Glasgow airport you travel to Paisley railway station and then take a bus to the airport.

Even when there is a rail link such as at Glasgow Prestwick airport, I usually ended up having to take the car to the airport and pay for airport parking.

How easy is it for you to get to an airport by rail?