Whether people like it or not, or are willing to admit it, there has already been a subtle shift in ethos of UK SAR Operations by the commercial operators. The military call it mission creep. In the past the priority was to get the casualty to a hospital, usually by utilising one equipped with an HLS. Already, we are seeing Bristow crews more frequently electing to drop the casualty at an airport for onward transfer via ambulance. This is a perfectly acceptable solution where injuries are not time critical and mitigates the issues of single-engine performance in urban HLSs. It may even be a quicker option than a low level grovel in marginal weather where the modern aircraft are equipped for a fast, IFR transit potentially in icing conditions (stand-fast AW189 clearance), assuming there is a slick ambulance transfer. The problem comes when there isn't a convenient airport and the weather or HLS isn't compatible with the best hospital option.
The numbers were expertly crunched to justify the 10-base solution. If senior members of the DfT had seen the map I saw recently which dramatically visualised the rescues carried out round the UK in recent years they would be very nervous about coverage down the east coast. Stats can be very forgiving when trying to justify a solution which saves money. I guarantee the press/public won't be as forgiving if and when said compromise gets exposed.