from my experience movietyme ship from the uk!!they just make people think they ship from the states direct to you-they dont!so you wont be hit with customs at all ,no matter how many you order.happy viewing
It shouldn't make a difference as they always come packaged separately. They may also arrive on different days depending on stock levels too. Unless you order a big box set you shouldn't have any problems.
Incidentally you may also get away with a box set - my Band Of Brothers got through fine. Also the general opinion is that they're posted from within the UK anyway.