Join Date: May 2012
Location: Munich, Algarve, Sussex or S.F Bay Area
Programs: Mucci, BA Gold, A3*Gold, LH SEN, HH Gold, Marriott Plat, IHG Plat Amb
Posts: 5,591
While the cheapest return tickets from the UK are usually completely non-changeable, many ex-EU tickets are semi-flex with change fees of €100-300, plus any fare difference.
If your need to change is because some unexpected emergency, BA have been known to be very reasonable in the past, even when a ticket is not normally changeable.