Be warned: although Alamo/Europcar are one of the few companies that say they allow Sunday return, this branch has only room for a handful of vehicles in its forecourt.
This means that when you try to return the car/van, there will be no spaces. Parking on the sidewalk or elsewhere near the office will earn you a £60 parking fine (like it did for me), plus a £27 surcharge from Europcar to process it.
Alamo Car Rental provide a car and van rental service.