its quite common to get the customs etc bill a few weeks later, what happens i believe is the importer pays the duty to get it thru customs then charges you later + their own handling/paperwork fee.
if you do get a bill and chances are you will id expect usually in the area of 25-30% on top of what the exporter put on the invoice. if you don't get the bill then you are in the minority. I would guess about one in 10 get thru with no fees (based on stuff i bought over the years from all over the world) although more expensive items (over £25) tend to get charged every time with smaller stuff such as a £4 phone charger from china getting past without (not worth the paper work maybe?)
watch out for exporters that offer to mark down the value of the goods, if customs open a box saying $50 on it and find a $1000 marker they will cease it without question and you may never see it if they are not happy when they start asking questions (i have never heard of it happen but potentially it can)
There are thresholds for the value of goods before duty is payable, details are on the HMRC website
There are a number of dodgy practices that people ask for or some sellers offer, eg making the customs declaration as a gift (which doesn't make it duty free, it increases the threshold), declaring items as commercial samples (fairly obvious when its sent to a private address, and this was/is a regular trick for pirate DVDs) or false valuations (not so clever when the true invoice is enclosed)
All of the above are known by HMRC and couriers and they look for them. The recipient is liable for false declarations and risks the goods being seized
For the courier noted he should have received a bill before the item was released. This thread is the first I have seen about fedexs strange dealings
