Thanks for your responses pert and westfw , this has kept me scratching my head for too long already.
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The oscillator is 12.000mz, but I tried swapping it for a 16.00 with no change in speed! (Go figure, I wonder if the chip isnt accessing the oscillator at all, relying on the internal timer instead??)
Meanwhile I see the Chinese supplier has now posted some additonal LIBRARY and HARDWARE software to add to the Arduino IDE to make these things work like a UNO. That .rar file generated Parsing errors in Linux but eventually worked on an old XP laptop.
You then need to select board type Wavcat Uno and yes, it now runs blink at the expected speed. However it also seems to have swapped some pin configuration around at the same time as these boards no longer work with an LCD shield when programmed as Wavcat Uno.
Either way this board doesn't meet my expectations of a basic UNO, we shouldn't have to load additional drivers to make it work like all its clone cousins, it should be interchangeable with all other UNO clones. Proof that you get what you pay for.
Refund requested via AliExpress. I would advise others to give the Wavcat or Wvacat a miss if you value your time, pay another 20 pence for something that meets the standards.