If I fly with a friend (not an instructor) how do I log the time
You cannot log the time at all. As you do not have a licence you do not have any privileges to act as commander of an aircraft (and therefore log P1) unless specifically approved to do so by an instructor as a part of a course of training. When an instructor does this, he/she takes responsibility for your actions during your solo sortie. The instructor must have had his/her solo restriction removed to do this.
P1 for time at the controls and P2 for the remainer?
According to the JARs, the type you are flying only requires one pilot (assumption, since you're doing your PPL) , therefore by definition you cannot log P2 (second pilot time) on this type at any time, notwithstanding the discussion ongoing on another thread regarding safety pilots.
And does this count (and how) towards the PPL 45 hours minimum? (In case this makes a difference I have about 2 hours solo).
Since you can't log it, it doesn't count.
cheers!
foggy.