Ok, please don`t take my word for it BUT i do think you are worrying over nothing.
I had(about 4 years ago in my naughtier years) 30 fake rolex watches seized from Thailand by customs.
I got a letter from TS asking me to sign a form saying iwouldnt do it again and where about did i get them e.t.c(i sent them to myself from Thailand) i never did send the letter back and i never heard anything again.
Please dont think i`m saying ignore it or anything, but i dont think you will get into trouble over 10 pairs of fake ugg boots(that you belived were genuine).
All the best anyway.
Its best to avoid buying goods like this full stop unless you know what you are buying. If you want Ugg boots buy them from the distributer. They are not to my knowledge available elsewhere , if they are they are fake like most other stuff coming from dodgy sources.
Dirty Rider is probably correct in that that aren`t really interested in capturing a small consignment of fake goods and taking you to court. It will cost too much to pursue . What they will do is moniter what comes through to your address from abroad and if it occures regularly then thay will act more than likely.
Ste