52049er
The Flight Crew gave up all those agreements years ago and now can do minimum time (usually 40 mins at LHR, less at LGW) turnarounds whilst staying on the same aircraft. The CC obviously needs to be changed at every LHR turn which, as you say, adds hugely to the operational complexity.
LHR EF is inflexible in terms of scheduling with crew sitting in CRC on long 2½ hour turnarounds when their days should be made so much shorter. Take for example CDG-LHR-MAN-LHR - looking at some random flights now. With their 2½ hour turnaround their "duty" - not including clear time - from chocks on to off is 6:40 when it could be 4:30 - with the latter including a 40 minute turnaround between CDG and MAN at LHR.