There is more to a DAB Columbus than just the headunit, you need a totally different and separate aerial. I am surprised they advised you the replacement would have DAB, since I would expect the opposite.

that's what I thought TBH and why I said i'd be happy to pay the extra to make it DAB compatible…  Just fed up of all of them giving me the wrong information.  

That's Skoda UK for you who seem to be a good source of mis-information.