As for the gantry cameras on the M1 from 6-10, my mates Dave's been through them above the NSL on numerous occasions and never had a NIP.
My mate Dave regularly drives the M25, 100+ and even got flashed but no ticket - variable speed limits off. Very recently he got flashed, 100+, by the Hadecs3 in Kent, again no ticket. He better watch out on the M4.