Good advice.
Its interesting to note that you can probably earn more per hour using your existing teaching skills than you ever will, teaching flying. You seem to have the bug; that will drive you on. You will need to diversify and have a day job as long as possible, only move into fulltime instructing when you can afford it.
You will need CPL knowledge and it makes little sense to go that far and not complete the CPL qualification especially if you wish to make it a career. If you just belong to an "aeroclub" and only want to suplement your flying with a little instruction then the PPL route is OK but there are few true aeroclubs these days.
from 57 hours to FI(R) will cost £20K - 25K. There are many like you who only want to instruct; having qualified, and made a large investment, the attraction of an airline job eventually wins unless you are too old!
Remember for every time you look up, wishing you were up there rather than being down here; when you fly professionally, there will be far more times when you are up there wishing you were down here!
Flying is great when you control when you do it! When others control it, it can be a bit like IT except you probably don't do your IT at 0200 in the morning on the backside of a cold airfield.