Pretty well any of the known makes will do - Pioneer, JVC, Sony - are all good.
BUT you said 'van'. Do you mean van as in four wheels and an engine, or do you mean caravan? If the latter then you would be well advised to stick to JVC or Pioneer. Caravan wiring does not provide a memory support supply that is permanently live, so using other makes may cause your radio to loose memories when the van is not in use. You will find that many caravan manufacturers use JVC or Pioneer as these two makes (usually) have non-volatile memory so whilst when power is off some may loose your audio settings (if you have made them different from default) these will retain station memories which is the 'otherwise nuisance.'
Remember you will also need a separate aerial for DAB. Assuming your existing radio is fed through the TV aerial there is no point in getting a replacement radio that has AM as the aerial amp will not pass the AM frequencies. If your existing aerial is one of those Vision Plus telescopic things on the side wall of the caravan behind the radio that will still work for AM and FM. In that situation you need to look at the TV aerial feed data as earlier versions do not pass the DAB frequencies. If the aerial amp is a VP3/4/5 then it will work with DAB: if the amp is just a simple box with one in and two outs for TV and radio it likely will not pass DAB. Also look at the aerial, whether it is a flying saucer or a directional, if it has orange or red lettering on it then it will work with DAB - again refer to the amp. If your caravan has a flying saucer type but NOT a Vision Plus then look up its specs on line as some (all?) of that type will only work with TV frequencies. If the TV/radio aerial meets all the criteria for working with DAB, you will need to fit an in-line splitter between the aerial amp and the radio as the radio has two different connectors for standard car radio and for DAB. This is one of those situations where Google is your friend!
Finally for the DAB section you can get a stick-on that goes on a nearby window and has an in-line amp but it may get shielded by the caravan body if the transmitter is in the 'wrong' direction. DAB aerials MUST be vertical. FM is 88-108MHz, DAB is around 205-230MHz, and TV in the UK is 470-796MHz at present but will be reduced to 470-700MHz in the future.