The 26-year-old defender signed for the Bucks in 2021 from Grantham Town.
A versatile defender who can play at either right-back or centre-back, Middleton started his career in the junior set-up at Doncaster Rovers, before moving to North Ferriby United, Scarborough and Harrogate Town.
Middleton went onto play four appearances for Buxton during a short loan spell, when he completed his transfer to Boston United.
After two years at Boston United, Middleton moved to Grantham Town, before leaving for Buxton one year later.
Buxton's manager, Steve Cunningham, has stated that Middleton's move to Cleethorpes Town was mutually beneficial, with Middleton favouring an opportunity to play more locally that suits his circumstances.