The truth lies somewhere between the opinions of Rod 1 and Cockeny Steve, I think that the composite aircraft have more than proved themselfs in the training role with the RAF, the Grob Tutor fleet has aircraft approaching 7000 hours without major structural issues.
It is the GA industry that is to blame for the composite is fragile myth because of the lack of understanding of the technology. I have seen a DA40 written off after a ground collision that could have been back in the air within weeks in the hands of a competent composite repair agency and another DA40 that was involved in a collision were the company disassembling the aircraft after the accident took a hacksaw to the main wing pin retaining locks, fortunately wiser people got hold of the aircraft before any further damage could be done and the aircraft is now back in the air.
Fuel is the real issue for flight training in Europe and the DA40 addresses this issue but the cost of the engine and avionics mitigate the fuel consumption.
What is needed is a simple robust basic trainer with a good intercom, modern radio and low fuel consumption, having seen 13,000 hour C152's with less structural issues than 300 hour SportCruser's I am a big fan of the C152 airframe but much less a fan of the engine, a re-engened 152 or even a FADEC controlled Lycoming would bring the fuel bill down to an acceptable level were the C152 would be more than a match for the less robust microlights in terms of overall operating cost.