Having done a PPL(A), I got told when I started on my PPL(H) that I'd need to have a separate logbook, or it would be too complicated for the CAA!!! Load of rubbish basically. It's personal choice. If you're keeping track of f/w flying hours, night hours, IMC hours, several helicopter type hours, instructing hours, and so on, you need some way of doing it that works. But that's all. It doesn't matter whether you do that in one logbook or ten.
I've always had two, and always used the small PPL ones. I stuck to that size when I needed a new logbook, as when I'm about 93 and they won't let me fly any more I want to get them leather-bound together so that I can sit in my armchair and look at them and dream. (Sad, innit?) However, I thought at one time of getting a commercial logbook with loads of columns (Jeppesen seemed to be the best) and re-labelling all the columns so that I could see any of the totals I personally needed at a glance. I still think that would be the ideal way...but that's only my personal preference.
So the bottom line it....you need to log it, but do it how you like.