I know this is a slight old thread but I wanted a similar thing as I'm using a universal remote with no next prev buttons to change between the bouquets. So, mine in now set up that the first time I press EPG it loads the channel list, press it again it changes so you can pick your bouquet.
I needed to edit keymap.XML so needed to ftp into my box. It's in usr/share/enigma2 folder. Transfer it over to your desktop and open it in notepad++ or similar. Look for EPGSelectActions .. In this section near the bottom it has KEY_EPG map this to "tv" instead of "epg".. Save and transfer back. Reboot your GUI or box and that's it.. Job done. Now when you press EPG it loads the channel list.. Press again it goes to the bouquets.. Press again back to the channel list.
Hope this helps as I find it much more user friendly now.
Steve