[5] He made three appearances and scored one goal for them in the Football Conference during the 1987–88 season, making his debut for the club in a 2–2 draw against Macclesfield Town at Moss Rose.

[6][7] Westley joined Wycombe Wanderers in the latter stages of 1987 for a fee of £7,500, making a scoring debut in a 2–1 away victory at Telford United.

[10] During his time at Kingstonian, he suffered a dislocated ankle and broken leg in three places, which subsequently cut his playing career short as he never fully recovered from the injury.

[11][12] While recovering from a broken leg, at the age of 28,[13] Westley was appointed as manager of Kingstonian in December 1996 after approaching the club about their vacant managerial post.

[14] His first two games as manager of the club both ended in 4–4 draws against Walton & Hersham and Harrow Borough,[13] with Westley saying "at the time, there was something raw and exciting about the team that I sent out.

[22] At this point, he also tried to arrange a merger with Kingstonian, citing the club's "Football League rated ground" as the reasoning behind his proposed idea, although it never happened due to "fans resistance".

[26][27] Shortly after his resignation, he became manager at Football Conference club Stevenage Borough in January 2003, signing a three-year contract.

[46] There were also question marks surrounding the discipline of the squad under Westley's control, as Stevenage received 14 red cards during the season, more than any other club in the league.

[47] A 2–0 defeat away to relegation-threatened Forest Green Rovers on the final day of the season meant that Stevenage failed to reach the play-offs, finishing sixth in the league table.

[52] Westley also brought in Michael Bostwick and Chris Beardsley, younger players who he had previously written about in his weekly column in The Non-League Paper.

[57] After leaving Rushden, Westley was appointed caretaker manager of Conference North club Kettering Town for the rest of the 2006–07 season on 20 April 2007.

[59] Kettering finished the season in second place[60] and they were beaten on penalties by Farsley Celtic in the play-off semi-final after a 1–1 aggregate scoreline over two legs.

[63] On his return, Westley stated he had come to "finish the job he started", referring to trying to guide the club into the Football League for the first time in its history.

[77] A 4–1 victory against Cambridge United on New Year's Day meant that Stevenage were positioned in first place in the league table for the first time in the season.

[124] He earned his first win as Preston manager in his fourth match in charge, securing a 1–0 home victory over Hartlepool United on 14 February 2012.

[130] At the end of the season, Westley criticised the club's "mediocre" mentality, stating the squad have "not got a clue what it takes to get success".

[131] Westley overhauled the playing squad ahead of the 2012–13 season;[132] Preston announced that 21 players would be leaving the club, 14 of which were released at the end of their contracts, while a further seven were transfer-listed.

[138] A day after Preston's 3–1 away defeat to Yeovil Town on 12 February 2013,[139] the club released a statement announcing Westley had been sacked.

[140] On his time at Preston, Westley stated he had to "slash the wage bill by 60 percent", and as a result the "re-building was well underway but the club lost confidence in me whilst I was doing it.

The club enjoyed a great deal of success before he left last year and we moved forwards significantly in his time here on several levels".

[143] On his return, Westley stated "I'm really happy to be back, the training ground is fantastic, the club just keeps moving forward.

[148] However, Stevenage never recovered from a poor start to the season, and despite a late run of six undefeated games ended the campaign in last-place and were therefore relegated into League Two, finishing eight points shy of safety.

[149] Westley was forced to largely rebuild the squad for the 2014–15 season, and brought in 15 new signings, including Dean Wells, Calvin Zola, and Charlie Lee.

He guided the team to a play-off place with a sixth-place finish, before they were beaten by Southend United 4–2 on aggregate in the semi-finals after conceding two goals in extra-time of the second leg fixture at Roots Hall.

[158] Shortly afterwards Westley again courted controversy after refusing to leave opposition manager Derek Adams's press conference.

[162][163][164] Caretaker-manager Michael Flynn managed to organise an unlikely escape from relegation for the "Exiles" after overseeing seven victories in the remaining 12 games of the 2016–17 season.

Yes, it happened under Flynny's management but I think anyone who is honest would say I did a very good job in working out a way of surviving and building a squad that would win the games at home to keep them in the League".

[167] Barnet chairman Anthony Kleanthous stated the move had come to fruition after Westley had been recommended to him by Peterborough United director of football, Barry Fry.

[168] Despite his previous ties with local rivals Stevenage, Westley had been identified as a "high impact manager" capable of changing Barnet's fortunes, with the club sitting bottom of League Two at the time of his appointment.

[19] Westley returned to Stevenage for a fourth time on 15 December 2019, four-and-a-half years after his last spell as manager of the club.