Hi Whinbush, sorry for the (very) late response.
This is something of a guess, but I think it's possible that your first three items date from 1999 to 2006. I collect certain types of Levi's denim shirts from the 1990's, and the labels often include dates (usually a "quarter" followed by the year, as in "3Q '94"). Sometimes, rather than a quarter being indicated, a month will be given. Anyway, your pant labels include: 1199 (which could indicate Nov. 1999); 0506 (which could indicate May 2006); and 0106 (which could indicate January 2006). The last pair made in the UK is a bit trickier for me. "2996" may be September 2, 1996 (seems pretty specific, though); or the "299" might indicate February 1999. ? Anyway, just thought I would offer a few ideas.