" An Aeroplane having a maximum total weight authorised not exceeding 390 kg, a wing loading at the maximum total weight authorised not exceeding 25 kg/sq.m, a maximum fuel capacity not exceeding 50 litres and which has been designed to carry not more than two persons".(Article 106 of the Air Navigation Order 1989).
Microlights come in different types and sizes
Check out "Types of Microlight" from my Homepage for photo's