I once worked for a particular African company (not naming any names, but they had 707s and DC10s), and did on one or two occasions see the same loadmaster on 10+ legs of a trip, all with 2/3 hour turns.
As DVR7R says, there's generally no duty time limits (which I, as an ops guy, always thought was absolutely ludicrous, because the consequences of an incorrectly locked pallet or misplaced pallet can be catastrophic).
A sense of humor would probably be essential.
As DVR7R says too, getting a UK based job as one will be hard, if not impossible, mainly due to the W&B all being done by local agents these days. MK Airlines used to have loadmasters.
That said, if you find someone who flies into less well 'equipped' places (certain parts of Africa and Asia being the prime candidate I'd think), then you might get lucky. Although it would probably mean either relocating or a long old commute to/from work.
I don't know if Cargolux have loadies or not for their B747s - they do do some stuff down to places in Africa with drilling equipment and stuff though, so it's possible that they would stick a loadie on for those sorts of flights.
I don't know if I can mention this (mod pls edit if so) but Mercator Aviation are a crewing recruitment company who might be able to point you in the right direction (google em). Before anyone panics, I have zero connection to said firm, just happened across them once in the past