Anyone nervous about upgrading to 10.11 might like to know that:

1. Flexcolor and a Flextight X1 scanner work just as normal, with an Apple FW400 to FW800 cable plugged into a FW to Thunderbolt adaptor.
2. Vuescan (which seems to have an update every time I open it; not sure if any are specific to El Capitan) continues to work fine with a Nikon 9000 and a Konica Minolta 5400 II. The Nikon uses a FW400 cable plugged into a FW400 to FW800 adaptor, itself plugged into a FW to Thunderbolt adaptor, and the KM5400 is a simple USB connection.
3. The Epson V850 did require a new software download from Epson, and it initially wouldn't open. It showed a dialog saying my scanner was linked to Image Capture (it never has been) and did I want to use it with TWAIN? The trick is to say yes to this - I had clicked on No the first few times thinking TWAIN was a plug-in for use with PS and the like. Well, Epson Scan must use it too. After saying Yes I have had no problems. Vuescan can also see and control the V850.