One of your more ridiculous threads AoG.
Thatcher does not have a birth anniversary in 2013 - and you didn't need to read Gromit's link to find out that was the criteria, it's in your own one. So either you didn't read that part, didn't understand it, or just decided to ignore it anyway.
Thatcher has already had commemorative stamps issued in the Falklands, and it's almost certain that she'll have one on the anniversary of her birth (which if I'm not mistaken would be in 2015).
I had heard of John Archer, but I'm not sure if I'd actually seen a picture of him before now. Mary Leaky and Norman Parkinson aren't people I recognised, though, and while I was aware of Elizabeth David I probably wouldn't have been able to place her face. Archer does, however, share a birth anniversary with the others and is thus entirely eligible. I don't know what you're complaining about.