'Digital Aerial' is a marketing term thats evolved since the introduction of digital services. Any TV aerial will pick up the digital services. If you're getting a good analogue signal now then the digital signal is likely to be OK.
Some aerials have a 'Balun' (a small transformer) built into them to help eliminate interference, which causes signal breakup and freezing.
As we are so close to digital switchover in the essex region, then my advise is to wait and see, if after switchover you're still getting problems you may need a better aerial.