Nice one, you've perfectly summarized my own opinions on importing, except that I've been lucky with the occasional order I've put it with Toysandfilms and not had any issues.
Amazon, whatever corporate monster it may be, does simplify importing anime relatively reliably without having to worry about additional import charges and all.
A couple of sites I would add would be
www.deepdiscount.com and
www.wowhd.co.uk (I think someone mentioned they're the same company) and I just checked and saw they have Nana for about £42 - I've never seen it cheaper so you could try them instead of Amazon to save some dosh:
Nana, Blu-ray, Anamorphic, Subtitled, Anime-Japanese, 816726021454
www.wowhd.co.uk
*Update: I just tried ordering on wowhd and that price didn't include the VAT and on review of their shipping policy it also doesn't include the custom charge, hence the lower price * sigh *, nevermind, I'll just from elsewhere I don't have to jump through hoops for.