I was in a similar situation. In my 50s and saw redundancy coming. So I did the CPL theory by distance learning during my last year of employment and then the FI course as soon as I was made redundant. I now instruct on my PPL, I can see no point in completing the CPL since instruction is the only paid flying that I intend to do (you can be paid to instruct on a PPL under EASA).
As a PPL with a reasonable amount of experience my goal was to put something back into flying and to give me something to do after finishing 'proper work', the money is secondary. As others have said you are most unlikely to make a living from PPL level instruction in the UK.
There is no age limit for instructors, so long as you keep your medical.
Hope that helps.
Last edited by wet wet wet; 26th Dec 2012 at 18:43.