The UK CAA FTLs limit their layover to a minimum of 48 hours. It's not because of kindness from the companies. The HK FTLs allow 3 Crew ULH with a 24 layover, so it will happen.
Dan - not sure CAP371 has that. More likely a combo of industrial / common sense and these days fatigue risk driven. Under EASA anything is up for grabs but certainly in the UK airlines are having to support what trip combo's they do with FRM etc etc.