Welcome, Theplantboy!
I'm going to start watering my arilbreds inabout 2-3 weeks when the night temps are a little cooler, here. It's a little hard to imagine when is best in London, or anyone succeeding with arilbreds there anyway! The likeliest ones to succeed there will probably accept watering much like regular tall beardeds, anyway. Juno Iris are completely out of my experience range.

Okay, thanks. I reckon holding off until Feb/March and then plunging the pots in water, wetting the compost around the roots but keeping the rhizomes dry. I'll report back on my blog!