Van der Graaf Generator, definitely.
If my memory serves me well we had to put our hands on the charged sphere at school and it made our hair stand up.
More a heavy rock band.
Okay, I sometimes struggle to pigeonhole bands. Yes I remember the term progressive was used a lot at the time but I was never sure exactly what it meant. (Yes, etc?)A friend who loved Status Quo claimed they were progressive at the time. I don't actually remember what VdGG sounded like: I imagine a Hawkwind type band- is that right?
The main prog bands were VdGG, Yes, King Crimson Yes and early Genesis. Quo were never prog. Hawkwind were / are the leading exponents of space rock, though had some prog elements especially on albums like Warrior on the Edge of Time...