My grandad was also in the CP. He was arrested during the General Strike and then blacklisted meaning a) him and his family was turfed out of their house which was owned by the employer and b) he then had to walk 6 miles a day to Aston before doing a shift on the presses and then walking back.
My dad told me that his dad cheered when Stalin sent the tanks into Hungary for exactly the same reason as yours supported Stalin. He died before I was born so I never got the chance to talk to him which I regret as I would have loved to.
I've asked on here before if there are any good histories or archival resources on the British CP rank and file (as opposed to the New Left Review group) in this period because the class composition, discipline and seriousness marks it out from much of what passes for the left. Even as late as when I started work it was the CP stewards in the factories who were the most serious, strategic and impressive.