Pic 3 may be P E Platt (Peter was it?) who is the only rider I can see featured in the results of the 1970 250 TT who was riding a Greeves.

Pic 2 looks like a 2 stroke single.  There were 4 Maicos in the results - we already know this isn't Borje Jansson and it certainly isn't Tommy Robb.  The other two riders on that brand were Harold Cosgrove and C Ward, so maybe one of them?

Pic 1 - Not a clue!  It isn't Marsovsky as he wasn't in the race.