Zizzi is one of my favourite chain restaurants in the UK. You can find it in most main cities and it's the same delicious food. I go there when I want a nice filling meal. The last branch I visited was the one in the O2 Arena (facing the North Greenwich station). There are a number of places to eat. Mainly non halal. This one has few vegetarian and sea food options. I liked the 20s illustration on the wall. 

and the metal sparkling simple chandelier. 

I usually go for the Arizona green tea with honey, but this branch didn't have it in the menu. They usually serve it in Manchester though. 

Of course had to order my usual Rustica Mezzo e Mezzo *yum*

It's a safe option if you want to have reliable place to eat.