Re: Buying from Overseas On-line
I'm afraid this is a very old and well known chestnut so sorry you were caught out by it, but TBH even a casual bit of research about buying from abroad would have forewarned you what to expect.
T-Shirts in particular are often just not worth it because of all the handling/shipping and customs charges. The US companies can't do anything about it, it's out of their hands. If they were upfront and honest they would state clearly that international orders WILL incur additional charges which they are not liable for. Usually such info is tucked away in a different part of the website. Your best bet for finding out reality for this and anything similar is to Google for "forums" concerning your situation.
e.g. Google "International T-shirt charges forum"
The 2nd item returned is entitled "Got stung by Customs" so off you go.
You will nearly always get a customs charge tagged on for certain purchases. The additional "handling charges" you get are a result of skulduggery by the site you are buying from.
International sites will happily quote and charge you for international shipping. What they then actually do is get the parcel over the sea to Blighty and then just throw it into the Royal Mail stream which for them is far cheaper than organising a courier. It's a bit like making a return phone call or sending an important letter to your friend and not putting a stamp on it.
Really the retailer you are buying from should be paying ALL postal costs end-to-end, but that makes their profits prohibitive and having to put high postal charges upfront on their website doesn't help sales does it. So the unscrupulous simply keep the "fine detail" in the Shipping/Delivery section of the website, are vague about what might happen, perhaps saying you might get a handling charge instead of saying you WILL get one and it WILL be in the order of £x.xx etc.
All this in mind, it doesn't mean we should not buy from abroad. You can make some fantastic savings that way. You just need to be clued up on what ALL the charges are likely to be. Some years ago I ordered a custom set of hybrid golf clubs with graphite shafts, full set with irons, metal woods, wedges, putter etc. Cost just $300 or thereabouts which is peanuts compared to a custom set here.