Renumeration as a PPL is always a touchy subject. I don't think you can charge a passenger for all that operating costs, however, they can be expected to cough up a preportion (50% if it's you and a pax), but make sure your insurance is in order.
Last year I was trying to help a friend out by offering a pleasure flight as a prize to help raise some money for a charity. I phoned the CAA to ask them what the legal position was and they basically told me the above. However, the CAA chap gave me an impression that if you do want to charge, then there won't be a problem unless you have an accident, when the insurance companies get involved. As a result, I decided not to offer the prize and as a result I don't ask people to contribute if I take them for a local bimble.
Just for your info, to charge for any flight, your plane needs a public CofA. You on the other hand need to have a CPL which entails the following;
1) Class 1 Medical
2) All the CPL writtens done. These can be done by distance learning, and are not as intensive as the Airline Transport exams.
3) 100 PIC
4) Sufficient night training (5 full stop landings and 1hr X Country)
5) 300 nm X-Country with 2 stops.
6) Completed a CPL course with a registered school and obviously passed the skills test (reckon on about £6000 for all that)
I know all this seems daunting to a PPL (congratulations by the way), but them der are de rules.