Not sure where you are posting from but the problems at the UK end are customs duties and the charge made by the carrier for collecting those duties.
Most US sellers go off on one when you ask them to mark a package as a "gift" - it is illegal to underdeclare the value of a package in the States - or so I have been told. So anyone buying from the US can expect to pay another 20% tax plus 8 to 15 GBP admin fee.
I have had quite a few packages from the Far East - Singapore, Hong Kong, Japan without any problems. One eBay seller has sent me packages marked as "gift" and wrapped in birthday paper!
The information from HM Customs:
For any type of purchased goods posted to the UK from outside the EU, import taxes and/or duty are payable by the receiver before delivery once the goods have arrived in the UK. The amount due is worked out based on the information shown on the Customs Declaration fixed to the package. Or if the value of the goods is over £2,000, the recipient will be sent a form C88 'Single Administrative Document' to complete and return to the postal depot before the package can be delivered.
If you're ordering or sending purchased goods (other than alcohol and tobacco) to the UK from another EU country then it's just like shopping in the UK:
there is no Customs Duty payable
there is no Import VAT payable, unless you're ordering or sending purchased goods from one of the EU 'Special Territories' and if the value of the goods is £15 or more
there is no Excise Duty to pay
[h=3]EU 'Special Territories'[/h]The EU 'Special Territories' are The Aland Islands (Finland), The Canary Islands (Spain), The Channel Islands (UK), The French Overseas Departments of Guadeloupe, French Guiana, Martinique and Reunion and Mount Athos also known as Agion Poros (Greece)
Commercial consignments of £15 or less are free from customs duty and import VAT. For example, goods purchased over the internet with an intrinsic value not exceeding £15, will not be charged any duty or VAT but this does not include alcohol, tobacco products, perfume or toilet waters. See paragraph 2.6, 2.7 and section 3.
If you are sent a gift with a value of £40 or less, and which complies with the rules shown in paragraph 2.5, it will be free from customs duty and import VAT, but this does not include alcohol, tobacco, perfumes and toilet waters.
Customs duty becomes payable if the value of the goods is over £135 but duty is waived if the amount of duty calculated is less than £9.
Customs Charges applicable
£0.01 to £15
No customs duty
No Import VAT
£15.01 to £135
No customs duty
Import VAT due
£135.01 and greater
Customs duty due, but waived if the amount calculated due is less than £9
Import VAT due
[h=2]2.4 Gifts[/h]Goods sent as a gift that are over £40 in value are liable to import VAT. Customs duty also becomes payable if the value of the goods is over £135 but is waived if the amount of duty calculated is less than £9. To qualify as a gift:
the customs declaration must be completed correctly
the gift must be sent from a private person outside the EU to a private person(s) in this country
there is no commercial or trade element and the gift has not been paid for either directly or indirectly
the gift is of an occasional nature only, for example, for a birthday or anniversary
Note: if you purchase goods from outside the EU to give as a gift to a relative or friend, whether or not addressed to that person, is treated as a ‘commercial consignment’ for which the import VAT relief threshold is £15 (paragraph 2.3 refers).
Now there are pages of this stuff on the net for which you need degrees in accountancy and international law, above are just the basics.