I've never heard 'bombed down', except where the 'down' is a preposition attached to another noun (and 'bombed' = 'went like a bomb': 'The car bombed down the road...'
The Sillitoe quote seems to be about speed. You can also use 'go down like a bomb' to denote success: 'The West End opening was a great success. The show went down like a bomb.'
Ther is a risk of confusion here, in a transatlantic context, as when a show 'bombs on Broadway' it doesn't go down like a bomb () it goes down like a lead Zeppelin ()