Your log book needs to meet the requirements of both ANO art.79 and JAR FCL 1.080 to be fully compliant.
Specifically, the times of departure and arrival are required under UK rules but not JAR (only date).
You will want to separately detail IFR time (which may be in VMC) and Instrument time (which may be under VFR - in VMC with foggles and a safety pilot).
The other requirements are mostly standard to all log books.
So, if your PPL log book meets those needs, or has extra columns that you can label up and total to comply, then you can carry on using it.
If you want to continue with a big professional log-book, just draw a line under the last entry, close it and transfer the totals to your new log book.
Multiple log books are a good idea for different classes of aircraft - fixed, rotary, glider etc, but better to keep one book for the same class or keeping column totals correct and traceable would become problematic.