Application to set aside a CCJ applicant claims large sum of cash paid

[Looch]

Hi I don't know if anyone can help.* I undertook some work for a self employed builder in 2017 and he failed to pay me.* I took h9m to court and attained a CCJ against him.* He then agreed a payment plan after the first bailiff visit and stuck to this at £300 per month for 7 months (albeit always late with payments).* He then stopped paying.* I then applied for another warrant for the full remaining amount of just under £3000.* He contested the amount owed so I sent a statement of account to the court.* I know the bailiff has been actively chasing him but now I have received a court application to set aside the debt raised by the builder.* His evidence is bank statements with the instalment amounts and a cash withdrawal of £2000 back in 2018.* Of course I have never received cash from him altho0ugh I suspect this is what he is suggesting.* Can I defend the CCJ and warrant as he has no receipt etc for the cash from me?
Thanks for any advice offered in advance as I am finding this really stressful.