I think when I signed up they said there was a three month period before a service but I'm sure mine was a month after I signed up
You'll need to double check but it isn't long and you should be alright
Yup you were right But there is an up front option.
Below extracted from PDF
Important Information About Your Service Care Plan
We are delighted that you are purchasing a Mercedes-Benz Service Care Plan. Our Plans have been developed to
give you real control over the way you pay for the servicing of your Mercedes-Benz or smart.
We know that you may have some questions about your new Service Care Plan, so we have provided answers
below to some of the most frequently asked questions:
When does the cover begin with my Service Care Plan?
The cover of your Service Care Plan begins on the “Commencing Date” shown on your Service Care Schedule
document. This will be the day that your Retailer has created your Plan for you.
If you have purchased two services paid for over 24 months or three services paid for over 36 months, the first service covered by your Plan must be at least three months after the Commencing Date.
If you have chosen any of our other options, including paying for your Plan up front in full, the first service can be carried out by your Retailer immediately.