Andrew wrote

Early 70s house, gable ended roof made from prefabricated trusses.
I have a problem with condensation in the roof space.

snip

On rolling back some of the insulation I see
that the outer leaf of bricks has been built up between each truss so
that it comes right up to the roofing felt. An even more effective
block to any ventilation. Is this normal practice?

No

Should I just remove these extra bricks and allow airflow through the
soffit vents?

Yes

A previous house had an airbrick high up in each gable end. Would that
be a good solution?

Yes - excellent idea.

Peter