I've learned a lot about Miele Dishwasher Draining, and the importance of a digit.
The issue was the dishwasher not draining, I didn't believe Teh Wisdom of Teh Internets, that it was the drain motor (£100, thank you) and investigated further. Ignoring the time I pulled the drain hose out while lifting the hoses pushing it back into situ (Nothing to see here, splash on by), I finally determined that the root cause appears to be a worn rubber gasket seal on the non-return valve. Looking up the part number, most places were around the
£50+ mark, I found a single supplier in foreigns, on eBay, who listed the gasket only, for €10. Only not only did they not ship to the UK, but they didn't even accept incoming queries on the item. Step forward a forumite in that country who kindly agreed to be the recipient and forwarder of this part, thank you again most kindly if you are reading this! Time will tell if I have made the correct diagnosis, but I think I have
Onto that digit. I had observed that Miele part numbers seem to use the last digit as an increment for the same item. I'd searched for the part number with a zero at the end, 1, 2 and 3 and achieved similar results on cost. What I hadn't done, is go up to "5" at the end or search on the Miele site for "non return valve" as then I would have the full item from them for £33, which would have been more acceptable and possibly easier in the long run. Who lives, may learn.