Sandwith began his career as a trainee at Carlisle United and made his League debut in October 1997. He then joined Barrow in May the following year, where he made fourteen appearances, scoring three goals.
Doncaster Rovers was his next stop, in 2001.
In November 2002, Sandwith moved to Halifax Town. Impressing a watching Lincoln City scout during his time at The Shay, he secured a £10,000 transfer to Sincil Bank in 2004. Moves to Macclesfield Town and Chester City followed before he signed for Weymouth in July 2008, moving onto Oxford United in the February of the following year.
He signed for Mansfield Town in the summer of 2010 and the versatile defender made thirty-three appearances last term but was released in June after missing the end of the season through injury.
Sandwith has been training with Trinity`s league rivals Eastwood Town in pre-season and has impressed the Badgers bosses with some assured performances.