20 miles really isn't far. It's less than half an hour in a car.
I'm not unsympathetic, I rent and will do for life unless I win the lottery. That's despite being a single parent so clearly much more able to get free stuff 
I've put myself on the waiting list with my local council but even where I am (small welsh town) I'm looking at about 10 years wait then an offer of a horrible house in a seriously deprived area.
Also, you're car insurance costs are far too high. Shop around and make sure you're no paying for optional extras such as breakdown cover, legal cover, key cover etc. My XDH had an accident in my old car and wrote it off, I still paid less than £300 the next year. You do have to do a lot of shoping around be very aware of every little bit of small print but it is worth it.
I know you we aware of how expensive your phone contracts are. (Where on earth forced you to take a 4 year contract I don't know, and if you worked in the industry then you know that there are many cheaper options available which still include free handsets for much shorter contracts, so I'm sure you've beaten yourself up enough about that one)
I never agree with the people who so breezily suggest 'just move' as it really isn't that simple but in your case I do think you should consider it. Not any distance away but it would definitely be worth looking for somewhere with better access to schools. You may not save money on rent but all that petrol cost vs 2 miles through muddy fields business would be solved.
Renting sucks balls a lot of the time so I totally understand your need got let off some steam but in all honesty, you're in a much better position than a lot of us so whilst it's not ideal it really could be worse.