To my surprise, I was called back by the Vat tech support people the very next day, but having been told that it would take a week, I didn't wait and registered as best I could. I think I've got it right. But they agree that the web pages for resistering for VAT MOSS are not easy to navigate.
And I've finished doing the software development. So now I know, for each of 28 countries, how much sales I make in each one, so in three months time, I should be able to use the VAT MOSS service and pay the right amount of VAT, which, I think, will be within a few percent of what I'd pay under the old rules (all at the UK 20% rate).
So why bother?
I think they've done this to get people like Amazon and Google. They're based wherever they say they're based, maybe in some low-tax country, and pay the taxes at that low rate. Under this new rule, they'll have to pay VAT on sales in the EU, even if they're based outside the EU. And if an EU country offers a low VAT rate (which is sort of against the EU rules, but you can have some things getting a special rate, like newspapers (why, I don't know)) then they'll still be paying the normal VAT rate on sales outside that low-rate country.
Anyway, as far as I'm concerned, I thnk it's done and dusted. Except I have a tough question to ask of my accountant - why didn't he tell me about this a couple of months ago?