How to word a 4 weekly standing order mandate?

Tenancy Types and Management

In the past, all our tenants have been paying rent on a calendar month basis.
I have a standard standing order mandate form, that i complete and get them to sign and then I take it to a branch of their bank and get the bank to check the account number and sort code is in order, soi that i know that all is OK.
However, I now have a new tenat who wishes to pay on a 4 weekly cycle as that is how she is paid.
How do I word the payment day?
My thinking is that as she is normally paid on a Friday, I pick the first Monday after that and then put "and every four weeks".
Would a bank accept and pay at those interval?

Thank you