I have said it before, but I think it is worth repeating.
“The principal means of avoiding collisions in uncontrolled airspace is “see and avoid”. Available evidence suggests that the effectiveness of “see and avoid” is questionable when used in isolation (i.e. not in conjunction with a radar service), implying an increased risk of failure to detect a loss of separation.”
That is what the CAA say.
The evidence is if you are very lucky you will first see another aircraft at 3 miles. At typical GA speeds you have less than 20 seconds after reaction time to see and avoid the collision.
Realistically if you are going to collide you probably will be unable to avoid the collision using "see and avoid". Please do not kid yourself otherwise. I did and I was wrong.
On the plus side you stand a much better chance of seeing aircraft turning towards you or of seeing gliders (who are likely to be constantly turning) and you should develop your see and avoid technique to avoid this type of traffic.
How can you improve your chances of missing other traffic.
Well it is something I thought a lot about. I have a number of suggestions concened with how and where you fly but (leaving those aside for another post)
TCAS clearly works but is expensive and if you are moving between different aircraft most will not have this fit.
Fortunately the mobile TCAS systems work.
I would not fly without one now - ever!
They are simple, reliable, and it is surprising how much traffic they pick up, that you dont see, but is within three miles.
IMO an investment worth every penny as long as you understand their limitations.