Ta for that - I'm sure on of our local SAAB Specialists will have a
suitable replacement that I can pick up tomorrow.
I want to replace the lot with good aftermarket material and have an
end to snapping these damn things.

The problem with the old Bosch CIS/K-Jet system is that the injectors
are manual - they are opened (continuously) by the pressure of the
fuel, not fired by ECU. To that end, the wider the bore, the lesser
the pressure for the same delivery of fuel? Or does the pressure
increase when the bore drops to the aperture of the injector opening
and crack the injector open. That's my dilema. I have found loads of
posts on forum boards where people have commissioned aftermarket hoses
for the CIS system, but they are very light on the technical detail.

I know years ago, I had this discussion with Grunff (now there's a
name from the past, alt.autos.saab-wise) and he commissioned a set
from a local hydraulic specialist. The guy I talked to today could not
drop down to microbore - his swaging machine would not go that small.
I've got a couple of leads to follow up tomorrow (on foot).

The size of the hose is not very important, but since the velocity of the fuel
flow in a larger hose is smaller, and because of Bernoulli's principle, there
will be less pressure loss with the same volumetric flow rate. Consequently,
there will be a slightly higher pressure at the injector, causing it to inject
slighty more fuel. To avoid this all hoses should be the same length and same
diameter.