I first saw the slipcased 'The history of English Racing Automobiles Limited' at McGills in Elizabeth St, Melbourne - not long after it was published. It was a stunning production with gorgeous enamel ERA replica grille badge adorning it and an equally stunning price. It was going to take a lot of weeks saving my $7 a week paper round pittance. As you can imagine it didn't happen.
I was a bingo caller (holiday times) in Blackpool at the time, but my weekly money would have been bigger than yours. Like you, I regret not buying the Weguelin book when it was published. I was tempted by a copy in a local shop -- surely you remember generalist bookshops?
Today, I'd buy an "update" of the original. Owing to passage of time, it would be a different book.