Must say that I find Easy relatively expensive compared to BA, Midland etc, but that FR are consistently cheap from STN.
I regularly use the STN-CRL service and it's usually about £25-40 depending how early you book.
The other factor that should be considered in booking low cost is that they can (and in my sometimes experience will) cancel following disruption, without offering any alternatives.
For this reason I will book Ryanair to Charleroi as the Eurostar offers a viable short notice back up, e.g. Stansted Express and tube to Waterloo or back direct from Gare du Midi.)
I will not fly Easy to Athens - BA or even LH would be my choice there, as they will get you there eventually.
When on business, that's an important consideration. It may not be for leisure.