The only UK retail brands which don't seem horrible are high-end department stores (Selfridges, etc.) and grocery stores, and neither really seems like a good background for running Apple retail.
There were two main kinds of stores -- pale imitations of Best Buy, Circuit City, and Microcenter (out in the suburbs/small towns) (which is ironic since those businesses have had serious problems in the US market now, too, 10 years later), and urban small stores. The smaller chain stores (Dixons high street locations) had very limited product selection and you had to wait in a queue to get a salesperson to handle your purchase, rather than staff out on the floor to push products (often on commission) and then take the purchase to the registers. The big stores mainly had cookers and other white goods/appliances, with really limited selection of anything tech. This was 2000-2002. EU stores were a lot better in my limited experience (NL and DE). The only way to actually buy computer parts was to go to fairly sketchy flea market type buildings or fairs, mail order, or a small number of independent shops (at least in London; never found anything outside London).
Staff were even less educated on products than at a Best Buy in the US today, terrifying. Even getting people to take a model number and look it up in their inventory system was a minor production.
I do however agree on some of your other points, such as poor selection and useless staff.
Price is set by willingness to pay. full stop. Cost for goods is almost always worked to, backwards, from price targets. Exchange rates don't enter into it, except as pertains to costs.
GBP prices remain 'close' to numeric USD, because people still buy products at those prices. Looking into why they do, leads to interesting questions and analysis about disposable income, taxes, psychology, etc - but it's largely irrelevant.
It is that way because it works.
Completely irrelevant to the discussion
You get it in the US. I remember it in every store. Initially I thought it was intimidating because I was not used to it. But after a few months and some great experiences I really enjoyed it.
You don't get it in the UK. High street stores, especially noticeable in places like shoe stores where you need service to complete a transaction. You could easily wait 10 minutes until someone was available to help you. And it could take another 10 minutes per pair of shoes you wanted to try on. So painful.