allowable Interest payments on unpaid rent

Rent Arrears

I am in the process of taking my tenant to court for unpaid rent, I have looked at my tenancy agreement provided by a letting agent I used to find and set up the tenancy, and then hand it over to me to manage. In the tenancy agreement it says:
"Overdue Rent: Payment of interest for the late payment of rent which is more than 14 days overdue at a rate of 3% per day that the payment is outstanding"
The tenant moved out on the 7 August owing £1500 in rent i haven't got a court date yet but if i was to use this it would be £45 per day interest so from move out date to now its 45 days that £3525 surly this cant be correct? I cant see any judge enforcing this. Should i try or should i not mention it and just claim the rent arrears? I think they will offer a payment plan of a small amount every month.