Re: SLMG operating costs (compared to, eg., microlight trikes)
Difficult to quantify against a micro trike because the usage of the two differ considerably. An SLMG of the pop up variety is inevitably a high performance sailplane with a selflaunch facility - they are not really practical for touring etc and are aimed at providing an alternative to aerotowing to suitable lift or regaining height in order to prevent a landout and to be able to return to the home airfield.
Engines are typically two strokes and are set up such that a constant climb is necessary with most to maintain the revs within limits - even throttling back will not permit a tru cruise in most of the types that I am familiar with.
Look at the webs sites for typical glider manufactures for more info - their websites can also be found easily if you can obtain access to a copy of Sailplane and Gliding.
Costs will include insurance and annual arc renewal, fuel costs are not high as this type of sailplane is flown predominantly "engine off" as a pure glider.
There are quite a few operating from gliding clubs within the UK