having read the above comments a few thoughts. While there are some very competant pilots around Microlights or otherwise there are also some complete idiots who have very little experience or ability.
Vmc with practice Ils and two pilots there should not be a problem, but change that to minimal VMC or Lowish cloud and a genuine ILS approach where the pilot of the one aircraft is glued visually to his instruments and you have a problem.
Mix in a dolop of Idiot pilot who doesnt really have a clue where he is and there are plenty about and you have a high collision risk.
But people will fly within the regulations they are given and exploit those regulations to the utmost.
So dont blame the pilots blame the regulators.
This thread like the one on gliders flying in IMC conditions without transponders shows a hightened potential risk for a collision.
In my opinion any ILS should carry a hub of NO GO airspace without radio permission. Infringe it and get the book thrown at you. But its the regulators at fault not the pilots whether they be microlights or otherwise.
Pace