Revenue: £87.1m (+23%)
Net profit: 7.9% Staff: 372
This LDC-backed mobility specialist this August snapped up Glamorgan Telecom Group in what it promised would be the first of a number of acquisitions following a £100m funding deal last year. Vodafone's Strategic Partner of the Year for 10 years running, Hampshire-based OneCom also counts Mitel, Nokia, Samsung, 8x8 and Apple among its vendor buddies. A lack of fresh accounts means that we have had to recycle its old numbers for calendar 2018, when revenues hit £87.1m.