Thanks guys for the good tips.
The dilution was 1:31 ('Dil.B') and I reversed the tank 5-6 times every 30 seconds or so, like I usually do with Ilford HP5 film.
Maybe that was too much here, but I figured that less agitation would not be enough given the age of my stock solution. This proves however that old HC-110 is still as good as new. Come to think of it, it's about twelve years old and by now the color is a deep brownish orange, but still transparent. I had bought a new bottle last month because I planned to dump the old one, but I can see now that this would be a shame. Perhaps I just need to shoot more film
Indeed Phil, I have the first (mechanical) version of the F1. Here is a picture of it. At first I was not too wild about the 'circle and needle' meter indication in the viewfinder, but it grows upon you after a while.