I made myself a routing jig for hinging doors today out of a piece of
architrave. It works OK for the doors themselves but of course I can't
get the full cut out of the door frames with it because of the rebate.

The only thing I can think of it to build another jig to do the frames
but this means carrying two jigs, resetting the router and the
possibility of mismatching cuts.

Any suggestions?

Buying the Trend jig is not on because of the need to have the hinges
set at the distances specified by the owner, which will vary from job
to job. Besides, the latest ones are (or were last time I looked) £70
for a four hole jig and £40 for a three.