The UK’s biggest private broadcaster is expected to announce that it’s taking high-definition versions of spin-off digital channels behind Sky’s pay-wall. Although audiences for HD versions of ITV2, ITV3 and ITV4 are small, CEO Adam Crozier is planting a flag for the future. Eventually all TV channels will be high-definition, which means ITV could become subscription only.

Meanwhile, the Financial Times reports that ITV is interested in buying Virgin Media’s 50% stake in UKTV, the pay-TV channels it runs with BBC Worldwide. UKTV runs 10 channels, including the popular Dave, which repackages recent BBC comedy shows. UKTV made £27.2 million profit in the first six months of 2010. Matthew Horsman of TV consultancy Mediatique envisages ITV putting its best older programmes together with recent BBC output, becoming a “Best of British” offer.

ITV is due to announce its half-year results tomorrow morning. RBS predicts that ITV will have an extra £120 million available to spend on programming on the back of operating profits rising to £156 million ($247 million) compared with just £46 million this time last year. Revenue is expected to have increased 9% to £995 million, says RBS.