Does anyone know if you can add DAB to the Swing radio? Be it something that plugs into the unit or a seperate receiver that the connects to the Aux input?

No point, you will get an RCD310DAB for less than the cost of buying an add on module from Pure or AutoDAB, etc. the RCD310 is identical to the Swing save for the illumination (blue screen, red buttons to all white depending on how new you can find). It's worth the compromise.

What about the aerial? I've seen some devices that splits the standard aerial signal between AM/FM and DAB. they also state that they only work with non-amplified aerials? The Rapid one is amplified is it not? I take it all the other functions would still work as they do with the Swing unit, i.e blotto the phone and music streaming along with the USB input?

Thanks for any help in advance

Whatever you get, you'll need an aerial. The £20 Autoleads aerials from Halfords, that stick inside the windscreen are perfectly acceptable and the head unit supplies them with power.

All other functions related to your Swing will remain the same.

You realise you will be listening to poorer quality than fm and often mono?

Extra choice of stations though.

I've always found DAB to be far superior to FM?

You realise you will be listening to poorer quality than fm and often mono?

Let's not get into this and take the OP off topic.