Siddall was educated at Ellesmere Port Grammar school; where he was spotted by a Bolton scout, together with Paul Jones and Neil Whatmore.
In September 1976, he moved north-east to join Sunderland for a £80,000 fee, intending to replace retiring club legend Jimmy Montgomery.
He was loaned out to Darlington during the 1980–81 season, who were managed by his former Sunderland boss Billy Elliott; Siddall played eight Fourth Division games at Feethams.
In August 1982, Siddall signed for John McGrath's Fourth Division Port Vale and went on to make 81 league appearances for the "Valiants" in a two spell.
[1] The first choice keeper in the 1982–83 promotion campaign, he was sidelined for three months after sustaining a knee injury in a 3–1 win over Bristol City at Ashton Gate on 27 December 1982; Neville Southall was signed on loan to take his place.
Despite only spending one month at Bloomfield Road, during his seven league games for the "Seasiders", Blackpool were the victor in six of them, which assisted in their finishing sixth in the Fourth Division.
He was also first-choice during 1987–88, making 38 appearances, but in 1988–89 he was dropped a couple of times in favour of his deputies, Gary Kelly and Vince O'Keefe.
[1] Former Port Vale teammate Robbie Earle praised Siddall's assurance and stated that he was "a confident guy who didn't suffer fools gladly".