The Executive Summary of the Ofcom report says (*emphasis mine*):
"1.3 The rules which apply in the UK set limits for the commercial public service broadcasters (PSBs) – Channel 3, Channel 4, S4C and Channel 5 - and all other commercial broadcasters. For example, there is a limit on the *average* number of minutes per hour of advertising across the day of 7 minutes an hour (off peak) for PSBs and 9 minutes an hour for all other broadcasters."
To enable programmes like Corrie to be bumper ad-fests, ITV often shows no adverts during less popular programmes (e.g. the public service obligation regional programmes shown in the graveyard Eastenders-is-on-BBC1 slot).