If you read the rules very very carefully, you should have your MOT test done before or on the expiary date of your current one to make sure.

Because technically you are now driving with no insurance, and if you have an acident or someone nicks your car your stuffed. No way will insurance pay out on it.

And in the future they will have cameras (some places already have them) that automatically read your numberplate and can tell if you have an MOT or insurance, and if you have neither instant fine, and get snapped on enough and the cops come knocking.