Cycling Techniques

I try and avoid waving people anywhere at all... if they got hit by someone/something else (undertaking cyclist?) it'd feel totally my fault, cos I'd been like "you're safe yo!"

I never wave people on for this very reason. if you wave them on and theres an incident they will blame you, you'll probably feel bad.
If you leave them to make their own decision it's their fault if it goes wrong. expect the worst and hope for the best.
Ride defensively and with confidence, motorists and pedestrians can spot a nervous rider a mile off.