acv4 you wrote .

"After about 2000 bets, my winners percentage is at 24%, showing a bank deficit of 12% on turnover at level stakes. I only bet on value runners - it's quite normal to see winners paying around 10-15/1 mark in my book. However, the 24% winning percentage hurt me in the end. I need about 27% to break even."

I mean this constructively.
Are you really backing "value runners" when from the figures you have given your average winner must be less than 3/1?
If that is the case how "normal" really are those 10/1 to 15/1 winners?
Maybe you need to have a close look at the odds you are getting. It may well be that a lot of the horses you back are not value. You also don't say whether your bets are on the tote or with the bookies. If they are on the tote at average odds of less than 3/1, then you would be showing a profit backing them at top fluctuation with the bookies - assuming they are not bush races, but Saturday/Wednesday metro races.