Here you go - I wrote this out on BC a few weeks ago, so just cutting and pasting here.
I know there is a lot of confusion about this so thought I would just outline what I've found out (and have confirmed with the tariff classification service this morning).
If you import cloth nappies from outside the EU, they are subject to import duty, as follows:
10.5% on the total paid (item plus shipping) NB not on the value so if you buy in a sale or buy wholesale, it is only on what you paid.
You don't have to pay VAT (as they are nappies and zero rated in the UK). They are not the same thing. You DO have to pay customs import duty, but not VAT.
You don't have to pay duty if the amount of the duty is £7 or less. The figure normally quoted is value of goods £18 but this is for VAT to apply and no VAT is payable on nappies anyway.
If you have to pay customs you also have to pay the processing fee to the parcel handler, normally around £8-£13 depending on who handles it.
All this applies only if your parcel is stopped - some get through with no customs being charged, in my experience around 50% of them are stopped.
The normal duty rate on clothes/textiles is 12%, so it is worth checking that they haven't applied that;, although the difference will be pennies unless your parcel is high value and probably not even worth reclaiming...
I hope that helps, and interesting to hear if anyone has anything to add...