Most of the mining cards never left the Far East which was why at the height of the boom retailers like OCUK were only getting a handful of cards in per week and some weeks none at all.I think that's what we now know. Even if you are generous and add up all the bay sales this year I bet it would not equate to the volume of cards people think were soaked up in the UK market.
People eventually got cards that wanted them, and being able to sell their old units for a high price equated to the upgrade costing way less. Miners buying up the older GPUs actually done them a favour.
The mining market in the UK is small fry by comparison and the cards simply were not available because they weren't arriving at retail in any great quantities. UK Miners no doubt bought some of those retail cards but the big fish in Asia were buying direct and with the cheaper power in Asia mining will still be profitable till ETH goes POS or the price drops even further so don't expect those cards on the bay just yet.