There are 25 multi-choice questions in the PPL Navigation examination and you have 90 minutes to complete the exam.
Questions 1 to 20 are 'Navigation' and are all based on the VFR flight you will be required to plan; many of them require accurate planning and completion of a navigation flight plan. Remember that you will not be permitted to take an electronic calculator, mobile phone or similar device into the exam room.
Questions 21 to 25 are 'Radio Navigation' questions - all of which are absolute gifts. You might even consider doing them first to get 20% 'in the bag' before you start drawing lines on your chart!
The chart used is indeed one which covers civilised areas of the UK, rather than the barren wastes of 't Nawrth, tha' knaws.
And remember, above all RTFQ!