Airfix Betta Bilda set (old construction toy, like Lego) (Pendeen TR19)

I found these in a big box of Lego. I don't know much about them but they appear to date from the early 1960s to mid 1970s. There are base pieces, blocks, windows and roof tiles. Some of the pieces are distorted (possibly from heat?) but a lot of them seem ok. Seems a shame to bin them if someone else can find a use for them.