Spike,
To save wasting money, I did things step by step at first.
1. Went for a trial PPL lesson to see if I liked it. Sounds like you've already made this decision
2. Did GAPAN aptitude test to see if I had the makings of a pilot (£150)
3. Did Class 1medical (£400)
To raise the cash for training, I used equity in my house but it sounds like you don't have that option. My brother took a career development loan of £30k from, I think, HSBC. He takes money when he needs it and starts paying back a year after he's finished training.
Hours building costs can be reduced by taking passengers who can pay their share. Remember that with a PPL, legally you have to bear your share of the costs.
To keep interest costs down I opened a VirginOne account. I was given a credit limit secured on my house. It meant that I only borrowed as each invoice became due and that kept interest down a bit. Also all my finances run through this account and that helps too. Savings keep the balance lower.
There's no way this is ever going to be cheap but you are right to be cautious about getting in too deep too soon. The really big costs don't arise until you start your IR so you'll need to be prepared for that.
Good luck!
AP