I believe you can petition for your own Bankruptcy with any level of debt, however the judge will only approve your petition if he/she feels it is your only / best option. Might be wrong so wait for an expert to advise you.
you can petition for your own bankrupcy with any level of debt but clearly it is only sensible if you have checked out all the options and have decided AND been advised it is the best solution for you.
For a creditor to make you bankrupt you must owe them a minimum of £750 - although this process is likely to cost them up to £2k to process the petition with legal fees etc.
Paul Johns Assisted Bankruptcy Specialists Reviva UK www.revivauk.com