Rob747,
If your intention is to do 'club level' PPL type instruction. You may want to wait 6 months or so, to let the present UK system settle.
I've recently put my ATPL theory course on 'pause' along with plans to do a FI and CPL course, because it is strongly rumoured that the new NPPL which is due to be introduced early next year, will have provision for NPPL level FI's who can be paid for instructing.
In short this may mean (NB; may mean) that it will not be necessary to hold a CPL to be a paid club instructor for NPPL instruction. The path for gaining a FI for the NPPL will also be alot easier than currently (No JAR CPL exams to do??).
Please note though that this is all being discussed by CAA and AOPA right now and may be very different when implimented (??). Also if you want to do JAR PPL or CPL instruction you will still need a JAR CPL/FI.
Good luck