DAB is not the easiest thing to fit, getting a good signal is difficult without nasty antennas stuck into the glass etc.
I have tried two solutions so far....
Sonichi S1000 DAB receiver from "Halfords", now this suprised me as even without the antenna reception was pretty dam good in my A2. The unit was mounted on the dash and power was fed from the fuse box. Then the aux lead ran to the RNS-E and went into the AUX input (enabled) on the RNS-E. Reception was pretty dam good with dropouts in the same places as my A7 with factory DAB. It improved even more with an active roof shark fin for DAB. But that was quite expensive compared to a glass mount. But my friend bought a Sonichi for his A3 and he said reception was poor until he used the supplied antenna, so maybe the A3 shields the signal better than my A2. But for £89.99 it's a good unit and the sound quality is excellent fed through the AUX input.
I now use the AutoDAB in car DAB receiver and it's a bit of a nightmare to be honest. It is not designed for the RNS-E, it is only for concert/symphony/chorus according to the blurb, but I thought I'd give it a try. It's not cheap at £189 and it comes with a glass mount antenna and it requires a MFSW to control it. When used with the RNS-E it comes in through the ZF connection and I have all sorts of signal issues with drop out, cross talk, brake pedal noise. I have been testing it for about 6 weeks and I'm just about there now with a solution that works, but I still get cross talk from channels that are close on the FM transmitting frequencies. Obviously it depends where I'm driving too as different stations kick in around the country. See if you can find a free bit of FM space between 87.5 and 108.5 that isn't used anywhere in the UK. The DAB reception is particularly flakey, nowehere near as good as the Sonichi or my A7, even with the roof antenna it drops out all over the place for no reason with just the message NO SIGNAL or POOR SIGNAL and it's not consistent. So my message to Connects 2 would be fix the reception issues and you may have a winning product.
So in summary, I like the sound quality and reception of the Sonichi, but I like the user interface of the AutoDAB.