You can't file a bankrupcy petition on them until you have won the case against them in court and given them time to pay. It would also cost you a few quid, good money after bad. cheapest and quickest way is the small claims court, it is cheap and easy. if they don't defend the case it will be found against them quickly, you can then ask them to send a bailif to collect.
They may try to defend the case and mess you arround for a while, and of course, when you win, they may have no assets for the bailif to seize.
if they go bust, you can claim unpaid wages and holiday from the government scheme, but it is capped at so much a week. Not sure of the current figure.
Good luck.