For people wanting to buy items that are published by a German Verlag, of course Amazon.de or eBay.de are the places to look. Postage from Germany is slower, more problematic and more costly when it comes to eBay sellers from Germany to Australia, and that's just one example.
However, UK sellers offer different things. The range of items is quite different, and the UK prices for UK produced items is better than the Fr or De prices for UK produced items. Postage from the UK is better than postage from Germany and Italy by a long shot.
If the contention is that sales on eBay.uk are going to be of a certain value, that needs to be looked at without preconception. Is the statement true or not true? We can't approach that question with honesty unless we assume it is in a state of "innocence" until we examine it. Presupposing it's not true, merely because eBay are assumed to be telling lies, is as biased as presupposing it must be true, merely becuase eBay are assumed to be telling the truth.
I would not accept your statement that someone "[is] likely to be cheated by a shill-bidding seller" merely because eBay UK has anonymous bidding. The opportunity may be there - and I know this is a subject dear to your heart, Philip - but we can't really close the gap between possibility and actuality merely by pointing to the possibility.
As an example, I recently bid on a particular German CD. The bidding went higher than I thought it would, and I was outbid on my maximum. I hadn't set up a snipe bid because I had to ensure I got that CD - if not from that seller, then from another. All right; being outbid, I shrugged my shoulders and bought the CD from a BIN listing for a little more than my maximum bid on the other listing. I was willing to pay a little extra because I'd dealt with that seller before and knew that his service was good. FAST postage to Australia from Germany (which is, as I've indicated, a bit of an exception from German sellers)... About an hour after the first item's bidding ended, I received a SCO from the first seller. Interesting! Could I assume the seller had been shill-bidding and been too clever for his own boots, outbidding my highest bid? Or could I assume the seller had more than one of the same item, and was using the SCO (quite legitimately) to move the second CD? I tend to think the latter is true, but in any case, it didn't matter, because as soon as I'd been outbid, I moved on to another seller.
As eBay becomes more and more a place where every seller sells similar items, you're going to see this happen increasingly, I think. No one's going to hang around for one seller's item when another seller has the same thing for a similar price. SCOs, except in the case of unique items or incredible bargains, might become largely irrelevant...