Thanks to all of you for your comments and suggestions, and especially to Wayne (who I have sent a PM this morning) - I haven't been online since last week as I've been busy on other things.
This is all very vexing, but I'll take a look at some of the other suggestions made, and see what comes of them.
The customs and import charges stuff into the UK is a bit of a mystery to me, as it doesn't always seem consistently applied. I recently bought a lovely little Proto 2000 0-6-0 on EBay from the US - would you believe I was the only bidder and picked it up, new and in original box, for just over £85 ? I was well pleased. The shipping and duty added another £40+, but even so, compared to some other "new" listing from Germany at well over £200, it was a bargain. Now, fitted with a WOWSteam decoder, it runs beautifully.
Now, I must get back to my other projects - an outdoor mobile cook station unit for the deck, and redecorating a bedroom. No trains for a while ... 
Thanks again to all of you,
Bob