For the F3, I'd have to delve into my logbook but defo over M2 - seem to remember it was a clean jet (no pylons) and before they wound back the fuel control units. I think it was M2.15 having just filled up from the Texaco, but it's all so very long ago now.
As for IAS, excursions above 750kts were commonplace at low level - the jet was incredibly quick. In the Falklands I've been 870kts low level over the sea with 2 Skyflash and 2 Sidewinders and the jet wanted to go faster (we decided to stop there). Many went faster than that and I even heard that 999 was achieved (or above as the numbers don't get any bigger). The fins of the Skyflash used to buzz around 600kts and then stop above that.
F2s were slower than F3s - less thrust, less fuel and aerodynamically draggier!
By the way, here is a picture of Fg Off Sammy Seal doing 825kts+ (the rear cockpit ASI stopped at 825)...
That's not my knee, I hasten to add!
LJ