If they decide to do this (and it is only a review that seems to be proposed, not action) then it would not be through a ban on sales, but through a change to the licensing permits which would limit hours of serving alcohol – and hence I imagine it would apply to lounges too.

On the other hand, if Heathrow sees this as a hit on its desirability as a transfer airport, with passengers choosing FRA, AMS and CDG instead, then I'm sure they'll be putting pressure on the government to pursue self-regulation, not licensing changes.