Pace, there are risks in every aspect of our lives and there's no point hypothesising about what could happen - If we did that we wouldn't get out of bed each morning. Yes, there's a risk (albeit tiny) that an airliner could collide with a microlight, glider, light aircraft, helicopter or whatever. Looking at the CAA's own data though suggests an area of much greater risk:
On 22/08/1985 a Boeing 737 suffered an uncontained engine failure and fire on take-off from Manchester - 55 fatalities
On 08/01/1989 a Boeing 737 crashed on approach to East Midlands after suffering engine problems - 47 fatalities
On 25/02/1994 a Viscount crashed following problems with engine and airframe icing near Uttoxeter - 1 fatality
On 12/01/1999 a Fokker F27 crashed into a house in Guernsey - 2 fatalities
On 14/09/1999 a Boeing 757 departed runway at Geirona, Spain following heavy landing in severe rainstorm and fuselage broke into three pieces - 1 fatality
On 02/05/2000 a Learjet caught fire on landing at Lyon, France after suffering engine problems - 2 fatalities
On 25/05/2000 a Shorts SD330 was struck by the wing of a MD80 that was taking off from Paris, France - 1 fatality
On 27/02/2001 a Shorts SD360 ditched in the Firth of Forth, UK following a double engine flameout - 2 fatalities.
(
Aviation Safety Statistics | SRG Safety Plan | Safety Regulation)
Looks to me like we need to stop airliners from using engines as they're clearly a major contributor to accidents!
Every time we fly we are taking a risk - engine failure, pilot incapacitation, structural failure, collision, etc. All we can do is to take sensible, considered, precautions.
It's always sobering to read the Airprox reports (latest is at
http://www.airproxboard.org.uk/docs/423/ukabbk19.pdf). If I'm reading this correctly, more than 50% of airproxes occurred within controlled airspace, so don't assume that talking to somebody removes all risks!