48. OCSL - £45.9m

The software and infrastructure player enjoyed a stellar FY11, with sales rising by more than a third and operating profit growing by a similar amount to almost £2m. The West Sussex-based firm has a sextet of key partners, comprising HP, Microsoft, VMware, Citrix, Symantec and Red Hat. Big-name clients include Dyson, River Island, Insight Investment and Virgin Atlantic.