Ok, a point to be made here.... from what I can make of your staking here you are loss chasing to try and make that 5% profit each time. That's a basic mistake and one of the most stupid ways of staking you can use, and nothing you can say will change any of our minds about that... it's dumb... end of.
If my calculations are correct it took 5 races to get your first winner, and 8 to get your second (unless you had Kauto Star). Now how much of your £1000 bank had already gone down the toilet before you finally got each winner. Do you have the balls to handle such losing runs on a regular basis, seeing your bank down to maybe a third or less before hitting that winner... what if that all important final bet was to fall? What if it was an odds on jolly and you needed to use the whole bank to get bcak your losses? No one but no one here with any sense would ever suggest this is a good way of backing horses.. why not? Because we've all been there, and had it crash and burn... and no amount of cockiness will see you through it. This is for your own good, and also to help stop anyone else from falling for your somewhat misplaced overconfidence.
My keyboard's running out of ink....