How easy is this to do, windscreen mounted type? I’ll go and have a look at how easy the van’s trims come out. The glove compartment is easy to remove, so feeding wires to the back of the head unit should be pretty straight forward.

I’ll be buying a new head unit, will the aerial get its power from the head unit, or do they require a separate 12v supply from the wiring harness or other source?

I fitted a Phillips DAB head unit to our Bongo. The head unit came with a DAB aerial with a magnetic base designed to attach to the body work, I fitted it behind the glove box and it works fine.

By windscreen mounted type, do you mean one of the thin film type, that comes with a DAB unit, or the antenna type, that sticks to the outside?
Neither should require power, AFAIK, they’re just passive antenna. I have a film type, stuck inside my Octavia’s screen, the cable running down the inside trim, then behind the dash. There’s no power required, and it should be the same for an external antenna.

Probably the wire type that sticks on to the windscreen. sounds like I can just pick up a head unit and aerial from Halfords and fit myself. if they only charge £29 for fitting, it must be pretty easy.

Do be aware the DAB is either on or off, depending on reception.

Not particularly impressed with the one in my wife’s car – factory fitted.

DAB might be on or off, but FM can be unbearable when it just breaks up into unintelligible white noise, with no clear reception for miles, like it does, or did, around Chippenham, Bath and Bristol. I would lose R2 on the outskirts of Chippenham, and not get a clear signal until close to the centre of Bath, that’s nearly twelve miles. My DAB, with a tiny little wire antenna stuck inside the windscreen gets 6music all the way into Bath and Bristol, with one tiny blank spot in Box. I’ve even driven down to Burnham-on-Sea, with clear digital reception all the way except for a short section along the M4 just south of the Avonmouth elevated section; that’s getting on for sixty miles.
If I could be arsed, I’d get a proper roof-mounted DAB antenna fitted, but it’s not a priority, if I lose reception, I just switch to the Pod.