I strongly suspect that it's an aerial problem.
In an ideal world, the lengths of your aerial elements should be exactly matched to the frequency of the incoming signal. Since each channel is on a different frequency you theoretically need a different aerial for every channel which you watch. (Imagine that lot on your roof!). That's clearly impractical, so we use aerials which provide only a 'rough match' to each of the incoming signals. That means that any aerial will be better at 'pulling in' some channels than others. Your aerial is probably poorly matched to the frequencies of the BBC group of channels. (The fact that you suffer the same problem with both your TV and your DVD recorder seems to confirm this)
When the received signal strength is 'borderline' it's often possible to view a channel normally, while still not being able to resolve the additional information encoded within the signal (which provides the programme details which you're referring to). Your aerial isn't providing your TV with a good enough signal to view this information for the BBC channels.
A cheap signal booster will almost certainly fix the problem.
Chris