Goatface's advice is the best route in my experience.
I have used the threat of a winding up order on three occasions over the last 30 years as a
PR Consultant (I recall it was a Section 221 order - but that may be out of date) and actually presented one to a company just once. You will appreciate that going that route with a client is the last resort!
The effect was electrifying in every case! Almost instant payment - on two occasions in folding money!
Go for it by finding out the Section and making the threat in writing; you can do that without incurring big lawyers money.