Jonny,
50k should be more than enough to train to become an instructor as you only need a CPL, not an IR. At the moment there is a desperate shortage of instructors but how the situation will be in 2009 is anyone's guess.
I shouldn't think your age should be a problem with getting instructional work.
However, even if you have enough capital to finance your training without taking on debt, you will still have to face up to the fact that instructor salaries are pants. You can expect to be on about £10-12k per annum, at least at first. Will you and your partner be able to continue to pay your mortgage and support your child?
TB