Albeit £750 is the threshold for issuing a winding up order it not that straight forward meaning you could never see your money at all.
Winding up orders can either force your client to pay you for the fear of loosing their business but get in line as other preferred creditors will be in front of you. Meaning the Inland Rev, banks, loans, preference share holders if any etc., So ensure you know what you are taking on before commencement. Once you start the ball rolling other creditors will panic and demand monies owed to them. A winding up order has to be advertise giving other debtors the opportunity to stake a claim for monies owed. You will find yourself at the bottom of the queue and may or maynot be paid at all.
Maybe the threat of such action may spur them into action!!!!! But if you've done your research and find that they have enough assets and are just not liquid in cash then your prospects for recovery are good.