Ray, good comment. I am way out of my depth wrt libraries and interrupts but this post gives me hope that there might be a way of using the WS2812B strip with a less fussy program than Neopixel library results in: NeoPixels Revealed: How to (not need to) generate precisely timed signals | josh.com
If you have time to scan read it, I'd be very grateful to hear if it looks worthy of pursuit. Simon