The pain did originally start on bending or straightening after
lifting stuff (i.e. a box of A4 paper), and about a month ago it felt
like it was starting to "lock" if I straightened it out - around the
same time I started to get a bad burning sensation in the elbow, but
it felt like a really nasty chemical burn, not the normal sort of pull
/ twist.

I've just had to kinda dangle it for the last few days, I can't move
it by itself, i'm having to flop it around with my good arm :-}

The worrying bit is the "good" arm has started to give that burning
sensation too...

Apart from the location, this all sounds somewhat like the symptoms of a
frozen shoulder. While I am highly reluctant to promote a magnetic bracelet,
they do actually work on *my* symptoms (I still get some intermittent pain,
but the mobility came back as predicted over a period of a year or so).
Being a rational scientist who knows that they can't possibly work, I came
up with three theories.

1: the bracelet acts as a counter irritant (i.e. distracts the processing
software)
2: magnetic field means there are fluctuating lateral forces on the nerves
in the wrist, and the mechanical stimulation affects the software
3: magnetic field acting on blood flow (electrical conductor) induces
electrical charge which affects something?

or maybe the placebo effect works even on unbelivers?