It was as a one-day cricketer that Hamblin was utilised most by Hampshire, making his debut in List A one-day cricket against Worcestershire at the Southampton in the 2001 Norwich Union League. He made a total of 48 appearances in one-day cricket for Hampshire until 2004.[6] He scored 656 runs in one-day cricket, at an average of 16.82; he made two half centuries, with a highest score of 61.[7] With the ball, he took 28 wickets at a bowling average of 32.39, with best figures of 4 for 29.[8] In June 2003, he featured in Hampshire's first-ever Twenty20 match, played against Sussex at Southampton in the Twenty20 Cup. In this match, he became Hampshire's first man-of-the-match in Twenty20 cricket, scoring a 27-ball 34 at the top of the order and sharing in an opening partnership of 66 with Derek Kenway.[9] He made a further four appearances in that season's competition, but did not feature in Twenty20 cricket the following season.[10] He was released by Hampshire at the end of the 2004 season, alongside several other players.[11]
In 2022, he took part in celebrations at Hambledon celebrating 250 years of first-class cricket, alongside Mark Nicholas and the actor Rory Kinnear, amongst others.[12]