One of my favourite outdoor (undercover) eateries in London was Yalla Yalla. The outdoor version in Shoreditch kept me warm (with outdoor heaters) and fed (with excellent street food from Beirut) throughout winter and summer. The only downside was the portaloos with alcohol handwash which wouldn't suit most people.
Nonetheless the delicious meats from spits, the excellent crunchy falafels, the flavoursome salads and dips, and the warm breads they'd refill for me for free (due to being a recurrent customer perhaps) kept me coming back and will always have a place in my heart.
I have many fond memories from eating here alone, eating with friends, and an end-of-year work celebration that turned into a Tuesday-drinkathon along High Street. I ate once in the central restaurant city location, but from then on this foodvan setup had me coming back every couple of months.