Problem Tenant

Possession - Section 8 and Section 21

Hi
I have tenants who have been in a property for five months. During this time rental payments have been sporadic and up to a month in arrears. I have also just received of noise nuisance from neighbouring properties.
The tenants signed a section 21 at the start of the tenancy agreeing to leave the property at the end of the six month let period.
I have informed the tenants that I will not be renewing the tenancy agreement and that they need to find alternative accomodation.
They have been advised by the council to stop paying the rent and not leave until I have obtained a court order for possession.
What are my next steps. The tenancy is due to end on the 3rd April. There are currently no arrears.