Just an update:
I have ordered last week a Bosch MAF sensor. It is the same as the one fitted to the Opel Corsa, (Holden Barina), and supports up to 370g/sec edit: 370kg/hr. airflow, which according to my calculations is good for ~115BHP. Should be perfect for my state of tune.
Going for the MAF route obviously, and I will have to fabricate a air filter and tubing etc. One thing I’m sure to have trouble with is the actual connection to the HIF44 SU, as I can’t weld.
Here is a image of the MAF, but this one is a Chinese knock-off.