my girlfriend said she was able to walk to the toilet and didn't need a catheter (I had never heard this could happen before).
TBH I had no idea what kind of epi I was getting but I was able to move around and didn't need a catheter (I didn't actually realise catheters where normal with epi's until I read this - derr). So it is certainly possible.

Also with the gas, it does take a bit of experimenting to get it to work well so sticking with it for a bit might help. I have heard lots of people say they try it once and throw it away cause they don't like it. With my first labour I used it and breathed way too deeply and threw up everywhere, but kept using it and found the right 'amount' of breathing to make it work.