Having had a bit of a look today I conclude that simply filing down the saddles and generally goofing around with the bridge units isn't going to be the way ahead as regards dropping the action ☹️
This because the amount I need to lower the strings would bring them right down to the front frame edge of the units, in fact I'd need to file a groove there too to lower the strings a little further. plus even if I did grind a load off saddles and bases, I'd end up with no break over angle at all at the bridge (there's not a great deal as they are).. whatever way you look at it, it isn't a good solution, see pics and you'll see what I mean.
This leaves the wood butcher option.. No I'm not going to try and dis-attach the neck and re set, it's too well fixed and getting it off intact and back on again would be a nightmare. The way to go is I think to carve out a lower 'platform' a few mm below the current body top surface. If I was a skillful carving wiz I could mark out around each unit and chop out a lovely individual shaped slot for each unit, that's not really an option so i'll have to do the next best thing and make a lowered recess for them all to sit on.
This may do me a favour in one way, I'll be able to run an 'earth' wire to the bridge units in a tidier fashion, possibly with a thin metal contact plate under the four of them?
Looks like i'll be practicing a bit of dremelling / carving /chopping on some random scrap wood before hitting the body itself.