Went out to Jessops and bought a set of thier cheap (really bad build) extension tubes.
Cheaper than one Canon extension tube with shipping on the www.
Would you believe Jessops had never heard of an L flash bracket ?
They said it was a professional accessory and they don't sell those !

This morning we had Red Admiral, Tortoiseshell, Comma, and Large White in the garden.
But then I was fitting the new brakes on my car.
In the afternoon thwy all went away as the breeze strengthened

So I hope to post some tomorrow.

30 years ago I was using a Zenit-EM, 135mm Tamron, 42mm screw extension tubes and two flashes, one on the body and one on the bracket.
No power adjustment, no diffusers, but one was a higher GN than the other so I got some fill in the artificial shadows.