Career
His most natural position is in the centre of midfield, although he has played as a defender. Armstrong has played in both professional and semi-professional teams in England and Scotland and has had international appearances for the Republic of Ireland U18 and U21 teams. Brighton and Hove Albion He started his career as a junior for Brighton & Hove Albion youth team, progressing into the first team in 1997.
In March 1998, he was picked for the Republic of Ireland under-21 team for a friendly game against the Czechoslovakian Republic.
Armstrong scored his first senior goal from a penalty in a game against Chester City in January 1999. Armstrong made over 50 league appearances with Brighton and Hove until he was released by Micky Adams in 2000. and Airdrie United He transferred to the Scottish leagues as a defender for (see The Last Ever Team) in the Scottish First Division, winning the Scottish Challenge Cup in the first two seasons he was there.
In his second season with, he helped the team finish second place in the First Division, but the club suffered serious financial problems and was liquidated on 1 May 2002. An Airdrie club was re-incarnated as Airdrie United by taking over Clydebank after their initial bid to stay in the Scottish Football League was given instead to Gretna.
Armstrong had a trial at Stranraer during the summer of 2002, but he decided to sign to Airdrie United for a season.
Airdrie missed out on promotion back to the First Division by a single point to Brechin. Armstrong scored 2 goals in 42 games for the new club before moving back to Sussex. Crawley Town Armstrong joined Crawley Town in 2003, then playing in the Southern League although a change in management saw Francis Vines take over and saw the club being promoted into the Conference National at the end of the 2003/04 season.
However, after three years at Crawley, the club suffered a financial crisis and went into administration in 2006, with many players leaving to join new clubs after not being paid for weeks.
Armstrong decided not to stay after 6 goals in 60 appearances with the club Eastbourne Borough Armstrong joined Eastbourne Borough from local Sussex team Crawley Town on 18 June 2006.
He was made club captain, bringing success to Eastbourne as they were promoted into the Conference National from the Conference South at the end of the 2007-2008 season via the play-offs, against Hampton & Richmond. Armstrong made several first team starts in the 2008/09 season with Eastbourne in the Conference National until he was attacked outside a public in Crawley, in late December 2008, causing a near-fatal blood clot in the brain, however he was lucky to recover and later helped Eastbourne complete their first season in the Conference and also the Sussex Senior Cup at the end of the season.
At the end of the 2009-2010 season, Armstrong was released by Eastbourne Borough Football Club. Crawley Town Southern League Cup Winners 2002-2003, 2003-2004 Southern League Championship Trophy 2003-2004, 2004-2005 Southern League Champions 2003-2004 Eastbourne Borough Conference South Play-off winners 2004-2005, 2007-2008.