you'll not want a two-stroke one.
The only point on which I disagree with the above post. I got my PPL(M) on a C series Shadow with a 503, flew for years a 447 engined Raven, then a 582 engined Blade, and also have had shares in 503 engined Thruster and Spectrum. All great aeroplanes, all bulletproof engines. Just because the modern generation of microlight instructors don't understand 2-strokes, does not make those engines, or the aeroplanes wrapped around them, bad.
I'd quite happily have a 582 engined X'Air or Sky Ranger, which should be purchaseable well below £20k (below £10k for the X'Air). Admittedly some configurations work better than others, but they're all perfectly good aeroplanes.
On the other hand, a Jabiru put me in a hedge once, and I've had a few others fail on me less catastrophically so I'm rather in agreement on that.
G