A few points:
1) I was on a RIS not 'limited' RIS
2) The controller was very busy hence I suspect he never noticed the other A/C, or did'nt have time to inform me. This is also why I never mentioned it to him.
3) Both incidents were stationary - very big - and growing fast in the field of vision. On the first incident with the twin, I had to dive so violently that everything loose in the cockpit became airbourne and I gritted my teeth for a fraction of a second as I waited for the impact on the vert stabiliser.
The one yesterday was not quite so close but I would guess 3-4 seconds to impact had I not descended.
I remember being taught during my ppl that the correct avoiding action was to increase power while inducing a 60' right bank turn. That would'nt have prevented a collision in either case here!