12 Bytes Software Services
Revenue: £345.9m (+33%)
Net profit margin: 2.9% Staff: 286
Thanks partly to a bumper £150m Microsoft Windows NHS win, this Leatherhead-based software licensing specialist saw revenue power up by a third to £345.9m in its year to 28 February 2019. Net profits bulged from £6.3m to £10m. Bolstered by its recent acquisition of Phoenix Software, Bytes Technology Group - owned by Johannesburg-listed IT group Altron - is now a £535m-revenue monster.