Forgot to add, rumour is general ban on using mobiles in hospitals will soon be lifted except in critical eqpt areas like ITU , theatres & cardiology as risk of interferance thought to depend on signal strength, say up to 30 metres from mobile, (or rear toilets)
One pax requested by another to not use her mobile during take-off run. Pax#1 scowled and continued her call well into the climb.
If the research is accurate British operators could enforce the rule by threatening the pax with 'endangering an aircraft / passengers' and confiscate the mobile during the flight. Unless a lawyer disagrees
I would also apply this threat to any pax who fails to pay attention to the pre-flight safety briefing