17. Northgate Managed Services - £141.6m

The IT services arm of the £850m-turnover Northgate Information Solutions group had a mixed FY12, with revenue growing 8.2 per cent as EBITDA dropped 10.4 per cent to £14.6m.

The company frequently appears on big-ticket public sector frameworks and contracts and just before the end of FY12 it reeled in a monster £170m contract to provide cloud services to the education sector in Northern Ireland, where Northgate MS has its registered headquarters. The firm claims the deal cements its status as the leading provider of ICT in the UK schools market. And the services company is upbeat about future growth prospects, claiming that, as of year-end, its order book carries an all-time high value of £303m.