Den Nobile advice.
 

OK, I have been winding the den nobs down as one by one they cease growing and show the last leaf on the cane. That will signal RO water only, and at a reduced level in the hope of encouraging flowers, not keikis.

Trouble is, a couple have decided to skip winter and go straight to spring, because they are starting to throw flower buds along the sides of some of their canes.

That makes me think that perhaps they shouldn't get a rest after all but go back to their weak fertiliser dose?

Advice would be appreciated.

I don't water or fertilize until I see new growth unless the canes look quite shrivelled then I water a bit

Well, as I say, that's m' plan, but what about the ones that are throwing flower buds?

Also is it OK to cut off the old shrivelled canes that bloomed last year, or are they still providing function?

Previously bloomed canes may bloom again if there are unbloomed nodes, and support the plant overall (they are in effect like pbulbs).
I would at the very least not withhold water from spiking plants.

Fhe point is REDUCED watering, not bone dry (I reserve tgat for aggregatum). You should give them a little water every 10 days or so.

So no fertiliser, reduced water and that applies even tho they are coming into flower?

This sounds exactly what I would say for a winter-blooming catasetum type. Reduced water to keep the cane from shriveling too much, but not so much as to spur growth, as nobile needs her beauty sleep ;)

Since this seems like a good thread to jump on...

This is the first winter I"ve had mine. They sent up plenty of new stalks and such durring the summer outside, but now that I"ve brought them in, sooooo many leaves are turning yellow as well as some of the stalks. The new kikie's aren't too shribbly (though have stopped growing) and all the main stalks are raiseny, even if green.

I'm not really sure what's normal for them.

Well, the trick with them to stop the fertiliser routine once the new canes have stopped growing. The key is that they have stopped when the new cane has a clear terminal leaf, as compared to the leaf in leaf structure of a growing cane.
In the dormant season, water sparingly. Not so much so that they shrivel, but much less than normal.

If you fertilise in the winter next year's canes will be prone to more keikis and less flowers.

And, the trick to stop the canes from growing any taller, is to pull the center leaf in the new growth. This is how the commercial growers produce plants with uniform height.