You could have seen the Ramones play at the Roundhouse in Brixton area on July 4, 1976!
It is interesting that you saw a lot of mohawks at that time. The tour guide was pretty adamant that mohawks were not around much at that time. I have seen some here and there in pictures from back then, and there were a few. Now, the clothing and piercings with safety pins started during that time frame.
That had to be an interesting thing to see back in 1976.