I know there were also brick ones, not just because my image searching tells me so, but because I have an old photo of one my grandparents and father had in London before that house (and 2 others they had at other times) was destroyed in a bombing. It was the only photo of any part of that house they had.
Anderson shelter were the common shelter.
I used to play in one in my Grandmothers back garden in North London.
I know there were also brick ones, not just because my image searching tells me so, but because I have an old photo of one my grandparents and father had in London before that house (and 2 others they had at other times) was destroyed in a bombing. It was the only photo of any part of that house they had.