You could always fork out for an airline ticket, go there in person to pick up the goods and reclaim VAT when you leave the country (works out OK if you are going to Europe anyway).
I was considering that option when I found out that Moulton dealers in the UK can't ship outside the UK (for some reason their bikes are more than twice the price here in Japan), but went for a different bike (Bike Friday) instead.
The other thing that comes to mind is that reshipping is widely used for eBay scams. Scammers recruit mules for internationally remailing goods purchased online using stolen credit cards / hacked PayPal accounts. You can see that any legitimate remailers, if they existed, wouldn't want to take those risks.
If the goods are shipped to a UK address, VAT would have to be charged, even though the ultimate recipient lives outside the UK. The standard rate is 20%, considerably more than consumption tax in JP or local sales taxes in the US. Unless you can find a way of reclaiming VAT, you'll end up paying both UK and Japanese taxes, which negates some of the advantages of shopping abroad.
I would (probably) be prepared to help as long as the items were not too expensive (to limit my risk). I wouldnt expect to make anything from any transactions. Also I fly to Tokyo on Mar 12th. Of course as Joewein says Vat would be charged in the UK.