There is talk in the SMEG+ Map and Speed Camera Update Procedure thread about firmware updates for problems with the DAB radio. Possibly this is one of the effects that is fixed.
It's still a dealer job if it's under warranty though. Although the chances are small, if the job goes tits-up and you brick your radio doing it yourself that would be your (expensive) problem. Let them take the responsibility.
I don't think these radios are anything special, seems to me a stand alone radio always gives better results.
My FM is very slow to change using the RDS when you drive out of range.
Then of course I have the DAB cutting out completely whenever I select reverse gear.
DAB remains on during reversing manoeuvres until the reversing sensors kick in when it drops to a very low level. I'm wondering whether there's something about your reversing sensor setup that's prompting the problem.
With apologies, on mine you can see the signal strength meter (crude though it is) drop to zero when reverse is selected. This happens when engine not running, ignition on and reverse gear. The sensors are not active in that situation.
Idiot dealer says it's normal. To be honest I can't be bothered fighting it.
But apart from that, my DAB works well. There was a problem of it being mono not stereo, but that did get fixed with the software upgrade.