Guy of Gisborne
If you are a carer (elderly parent, partner requiring assistance, child under 18 etc) you qualify for RtR (Right to Request) PTWK (Part Time Working). As explained this will give you the same week (75%) or the same two weeks (50%) off every month. The requests are made annually, and in recent years I have never heard of a valid one being denied.
Otherwise it's Aspirational Part Time Working (APTWK) which is available to everyone, even those simply wishing to reduce their tax burden! These are the 'two month on, one month off' variety.
Very glad to hear your ex-colleagues seem unanimous in describing BA as the UK's airline of choice. It genuinely is an excellent employer in many respects. Any moaning is normally about fairly trivial stuff in the grand scheme of things!