I did FIC course over the winter and got a part time weekend FI job at a club I have been a member of for a number of years. In four months I have flown 75 hours. Don't seem like a great deal but I have already learnt a lot and improved my flying. And I have got paid for it which is a big step in the right direction after years of paying to fly.
Typically you can expect about £12-£15 per flying hour in terms of pay for teaching PPL. You maybe lucky and get some kind of retainer that might be in the region of £15 per day. You will earn nothing when the weather keeps you on the ground but you will get some hours in the logbook and there seems to be a shortage of FI's around the south of England at the moment.
I say go and do the course if you can afford it. It can only help you realise your ambition of making it to the flight deck.