I've just read the AAIB report; as Peter says the aircraft was a touring motor glider. So more akin to a powered aircraft than a sailplane. I think current licencing distinguishes between self-launching sailplanes and touring motor gliders. I flew a Falke while doing my instructor training – not much to write home about.
Sailplanes and motors are now rather messy. Most self-sustainer engines are retractable. At one time the engine moved out on a pylon with direct drive to a propeller and is normally air start, as is my Nimbus 3DT. Some self-launchers extend the propeller but the engine stays in the fuselage, driving via a belt. This simplifies the pylon design, but is primarily for noise reasons. There are sailplanes that have a motor in the nose and a small propeller at the front where the blades fold back into recesses when not being used.
Tradtionally motors were 2-stroke petrol. But there are now also small jets and of course electric. The jets are impressive, but have the problem of inefficiency inherent in small gas turbines. Electric is a mixed bag. It promises much but so far doesn't quite seem to deliver. And of course battery fires are an ever present problem. There have been a number on the ground but I haven't heard of one in the air, as yet.
Andrew