Looking for solictor for dispute with recruitment agency

we have to recover debts from a recruitment firm. this is an undisputed amount which end client has fully agreed to pay. however, the middle party which is recruitment firm is holding the funds.

as per the investigation the direct Statutory Demand notice can be issues if the amount is undisputed and more than £750.

we are looking for a solicitor to draft a strong letter to the recruitment agency. also in case it is requried to go to court then solicitor can also be required to appear in the court as well.