The seller had it down as elm, which is why i was interested, but I don't think they were actively trying to mislead or anything.
It was a £20 bit of wood, which I can still use as oak, but just isn't as interesting to me as if it had have been elm.
The process of learning about the medullary rays must have been worth at least 10% of my spend anyhow!
Thanks to all for your assistance!