Cotswold Cameras

Looking on their website a sigma lens which I am interested in buying is cheaper than UK authorized dealers. I know that Cotswold are grey importers but I read this in their terms and conditions:
"Focusing issue for 3rd party lenses - 3rd party lenses (Tamron, Sigma, and Tokina, etc) often require calibration to work correctly with your camera"
and
"Firmware/software issues - We cannot guarantee the firmware version of our products and whether they can be updated."
Has anyone had experience of either of these issues, are they a problem?
Thanks in advance
"Focusing issue for 3rd party lenses - 3rd party lenses (Tamron, Sigma, and Tokina, etc) often require calibration to work correctly with your camera"
and
"Firmware/software issues - We cannot guarantee the firmware version of our products and whether they can be updated."
Has anyone had experience of either of these issues, are they a problem?
Thanks in advance