The knobs arrived in the post yesterday, but I wasn't home, so I nipped down to the post office this morning to collect them. The top knob was easy to remove, bit the bottom one didn't look like it wanted to come off. After much pulling and twisting of the knob it wouldn't come off. I decided to have a go at taking the RNS-e apart. Took a while, but once I got the front off and the bit behind the screen out it became clear that the volume knob does not come out without removing the front of the unit. There's a fat end on the back of it and it pushes through from the back to the front. The volume knob is just a straight swap, but the top one needed a bit of DIY as it stuck out too far if left as it was. I've hacked most of the inside out of it, but it is still a bit far out. I might give it another bit of a trim on the inside and attach it with a bit of silicone onto the clip. Probably doesn't make much sense inless you can see what I'm talking about. I've taken a few photos and will post them a bit later.