Now I look its actually the Lekato set, but looking at them they are identical apart from the logo, so I assume they are the same thing
https://lekatodeal.com/en-uk/products/wireless-5-8ghz-microphone-system-plug-on-xlr-transmitter-receiver
They are available cheaper than that.
Also found out that if you leave them on so they run out (they don't auto switch off) and forget to plug them in before a gig, 25 minutes being plugged in (they have one of those 2 way charging leads so you can do both together) onto a USB power bank is enough to get you through 1hr and 20 minutes of the first set, without them getting to the flashing stage (not sure how much longer, we plugged them in during the 20 minute break and lasted the next hour and a bit).
I would say that the only downside that we have noticed is that they are slightly wider than most microphones, so if you want to take them out of a microphone stand while you are singing, you need to pull the mic out, rather than slide the mic up.