Many local authorities manage on street parking in the UK, with an increasing number now insisting that you apply for a vehicle specific parking permit. Each local authority has its own rules/guidelines for this. You will need to check on the relevant website.
There are normally two pieces of documentation you need to obtain from LeasePlan. Authorities generally require proof of ownership of the vehicle in the form of a copy of the registration document (V5) and a letter confirming that the car is issued to you for your use as a company car.