I record off-air TV using Windows Media Centre. Those channels that broadcast in HD do so over the DVB-T2 standard, and in the UK at the moment that means H.264 in the transport stream. Media Centre wraps them as .WTV file which are almost unusable (other than playing back). You can't even re-wrap them to the earlier .dvr-ms format that other PVRs use (and is more convertible)
But, it turns out that the new version of Handbrake can handle them and convert them to vanilla H.264 with lots of pre-sets for iPad and other platform. Then you can use Quicktime to trim them (remove ad-breaks etc).