Contract End Notifications

In the UK it’s a requirement for providers to inform customers that their contract is coming to end

I’d like to specify a contract end date on each service, and have this be auto-populated with a date based on the start date when the service is created i.e. months after billing start date. This field should also be possible to be left blank for non-contracted customers

at the end of the contract an email template is sent automatically to the customer to inform them of the contract period coming to an end and what the implication for that is