I was just looking at the bottom division league table from 2002/03 for no other reason than that was the last season we spent in the bottom 2 divisions.
17 of the 24 teams in that division that season subsequently experienced non-league football. 7 have since returned. Included in the 10 that never came back are Rushden & Diamonds, Hartlepool and Wrexham, who were the top 3 that season. Rushden lasted 1 season and Wrexham managed 2 in League One. Hartlepool made the playoffs twice, losing in one final, then were relegated.
The other team promoted with R&D, Wrexham and Hartlepool were Bournemouth, in the playoffs. It's safe to say that they enjoyed wildly different fortunes to the 3 that won automatic promotion!