What's the difference between Q1 & Q2?
1&2 - yes. Twice so far. One on the London Heliroute approaching Isle of Dogs from the West at 1400 ft; one N of Gatwick, heading W into EGKR at 1300ft.
Never hit a drone. Yet.
The answer to 4 - both the above. Also I was asked by ATC, when over London on H7, whether I could see something as they had a primary radar return. I saw a drone a couple of hundred feet above, so it must have been large (not a cheap toy, though clearly not a professional operator)
Had a bird come close once on climb-out. I'd guess 100ft before it turned to avoid me.
Never hit a bird. Yet.