Murph,
OK so in your opinion, can all the hours the Blackhawk has flown be used to quantify the "extremely remote" possibility of having to fly with no oil in the MGB of the S92 seeing they do use a different but simlilar MGB
No! they are not the same gearbox - they are SIMILAR. Where do you draw the line between similar and same? They are both modular, they both have a similar configuration, they both use similar philosophies, they both look vaguely similar, but they are not the same. To some degree or other, all large twin engined helicopters have 'similar' gearboxes.
SS5 is up to 4m (rough,) SS6 is 4-6m (very rough.) Personally, I don't believe anyone would consider their float certification basis when considering the option to ditch, and if they do then they clearly don't understand the criteria for 'land immediately' (That's not in any way a comment on the Cougar crew - just the remarks above.)