Two steps forward and three steps back. I was gearing up to replace the windscreen scuttle, but started looking in detail at the corrosion around the edges. And then this happened.
I think it was the right decision. Surface corrosion verging on the serious inside the A pillars.
Cleaned up with some rust treatment:
The A post external flange and the roof skin are machine roller welded. No drilling out the spots here. Going to have to be extremely careful removing the old gutter to avoid damaging the roof skin.