Sandwith began his career as a Youth Trainee at Carlisle United and went on to sign professional terms with them, making his league debut in October 1997.

A series of impressive performances began to draw attention and, having scored against them in the Football League Trophy earlier in the season, Lincoln City paid £10,000 for his services in March 2004.

Ex-Chester manager Mark Wright was a big admirer of Sandwith, stating that he is "undoubtedly one of the best players in this league at delivering a ball with his left foot, from free-kicks and corners".

[1] However, he returned to the starting line-up against Notts County on 19 January 2008 and he regularly figured in the first–team in the closing months of the season, leading to him being offered a new contract at the end of the campaign.

Sandwith joined Mansfield Town by signing a one-year deal on 28 May 2010 after his release from Oxford United.