Hi Thank you for your question and welcome.
My name is ***** ***** I will assist you.
There are no specific guidelines but you would like to regulation 17 of Commercial Agents Regulations 1993.
On the basis that you have brought in customers the regulations suggest that as a starting point it should be a payment of 1 years commission calculated as a an average of the previous 5 years.
Do you have a contract with them? Kind regards