Many thanks, yes, I thought a transistor could be the easiest option to do the switching. Not much more to tell you really, just has to be simple, cheap and few components. The flash rate can be quite fast, so a cap could be included to help with this. I did see a circuit years ago where they used a small flashing led to drive a BD139 or similar to then switch the main LED, but since then, these COB units have emerged and may require something different, but a transistor such as the one mention ed should cover it, I would think.