On the 1.9 Digijet FI there is an electrically heated "cold start" air
valve located on top of the right cylinder head. It is  possible  that
this is stuck closed, and indeed, not allowing enough air into the cold
engine to increase the rpm.

Easy to check, just remove the metal coolant crossover pipe bracket nuts
and move it out of the way, and take off the air cleaner/AFM.  You will
see it, and it will have a hose on it that goes into the rubber intake
elbow as well as an electrical connector.  Remove it, and when it's cold
you should be able to see light through it. Throw it into the freezer
for 15 min and it should be open wide, there is a picture  of this in
the Bentley.  If it is stuck shut you might  be able  to free it up with
some Gumout, but you may just want to replace it since you are on a
trip.

Good luck!

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Driven since 1969)
'74 MGB GT (Restoring)

Assisting on Restoration:
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Parts cars:
'68 & '73 MGB, '67 MGB GT