[1] He lost in the last 64 of the 2011 UK Open after falling to Michael van Gerwen 9 legs to 2, after beating Stephen Hardy and Tony Ayres.
[3] His best result of 2012 was reaching the quarter-finals of the sixth UK Open Qualifier where he lost 6–2 to Ian White.
[7] The rest of the year proved to be disappointing for Howson as he failed to qualify for any European Tour events and could not advance beyond the last 64 in the 14 Players Championships he competed in.
[11] Howson failed to qualify for the UK Open for the first time but made the most out of an appearance at the final Players Championship of the year with wins over Mark Dudbridge, Terry Jenkins, Keegan Brown, and Christian Kist to reach his second career PDC quarter-final, where he lost 6–4 against Simon Whitlock.
[12][13] Howson played in all 16 Challenge Tour events in 2015, with his best result being a quarter-final exit in the sixth tournament.