Under EU-OPS the rules are different for aircraft with less than 19 pax. The starting point is 120 mins, with a possibility of extension to 180 mins. There is nothing actually laid down about requirements for the 180 mins approval, you just have to satisfy your local CAA that yuo can operate safely. I think this is what GJL have got.
For private ops there is no laid down distance from alternate. A lot of operators out there who haven't even thought about what is or is not sensible - they only look at distance to destination as if there were alternates every few miles..
