I've not encountered 'ghosting' since the digital switchover but I assume that the cause is still the same as with analogue signals. i.e. it comes about because your aerial is receiving signals via two different paths.
If the problem persists I'd advise getting the alignment of the aerial checked (or getting a better aerial with a narrower angle of acceptance for incoming signals). However, by chance, I noticed a post earlier this eveningstating that the Northern Lights might be visible in the northernmost parts of the UK tonight. The atmospheric conditions which result in such displays also result in what radio enthusiasts call 'lifts', whereby radio (and TV) signals are bounced off the ionosphere (as well as following their normal direct paths). Such a 'lift' could well be the cause of your problem; if so, it will only last a few hours.
Chris