Jobsworth
I did what you are doing right now for years. I am eleven years older than you and have JUST decided to go for it. You'll see the numerous answers to my question posted on the Wannabes board. Obviously the sooner the better but unlike myself and many other wannabes here, you have a several years ahead of you to get into the game. So start saving your pennies everywhere you can and get yourself a plan. Just think, a five-year plan will have you graduating with a 'frozen'ATPL by the time you're 30. I will be almost 38 (all being well) when I get to that stage.
If you carry on like you are, you're going to can the idea and probably never be happy in a career. Everytime you're doing a job in a different area you will be wondering 'what if'. It will take a lot of money it's true. Just focus on the fact that you don't have to pay it all at once. There's now a modular route so you can keep your day job for much of the process.
Anyway, you will be getting this advice from a number of sources so I'll finish there.
Think positive and ensure you get what you want. Best wishes etc...
Nigel