I didn't get a chance to welcome you when you joined, (due to a little unpleasantness going on with my colon, at the hospital), so

My guess would be that the test kit is hung in customs at the UK port of entry. I recently imported a PDA/phone from Cloves, in the UK, and it took about two weeks to receive it, despite using the fastest shipping method I could find. All but a few days of that time was spent while it sat in customs, waiting for someone to process it.
Once you get the sample back to the lab, you will be able to receive your test results by e-mail, so that will save having to wait for a letter to get through the mails, at least.
Again, welcome aboard, and good luck with the test.
Tex (Wayne)