Just a quick overview of my experiences getting stuff to the UK.
JJ is fantastic and nothing has been stopped yet. The first port of call for any purchaser. Thanks mate
Animeniacs have had a few packages stopped (roughly 1 in 4) but I order large bundles at once so this figure may be unreliable. They don't put the full value on the declaration, rather they state a nominal amount ($68 at the moment). Frankly the savings in getting a decent price for several dvdsets outweigh any customs duty significantly.
Animekrazy are a bit more expensive in terms of sets but also will write whatever amount on the customs form if you ask them to.
Dvdboxoffice are usually pretty good at avoiding customs, maybe 1 in 10 gets caught. Don't have too much anime in stock though, lots has to be ordered in.
Dvdsoon.com are very good as they label ALL packages at a value of $12 no matter the size. The only problem with them (they are quite a bit cheaper than Dvdboxoffice) is they charge your credit card when the order is placed rather than when it is dispatched and it can take a while for them to order in stock.
Ebay tends to depend on what instructions you give the person sending the set, ask for a low (under £18) declaration and you should be fine. However auctions tend to cost more than the better suppliers so I've stopped using them.
The runup to christmas is usually the worst period in the year for customs checks because nowadays so many people order gifts from overseas so a lot of attention is paid to VAT fraud rather than drugs, etc. The reason some of the charges are so high is not because of the VAT being claimed but rather that Post Office/Parcelforce place a huge markup on paying the customs charges during delivery, about 75%-115% I think with a minimum charge of £8.
Still, with the exchange rate at a cracking $1.74 to the pound its certainly worthwhile getting stuff at the moment, I particularly recommend the excellent FX Noir set, FX GTO and the FLCL dvds.
Cheers,
Neil