Yeah, it's not the cheapest but for a treat I really like it. Loads of fruit options for the base and also different crumble toppings then a few different custards/ice creams for on top as well. Think they do some other stuff like cheesecake as well.
If you're happy with Indian food and a slight wander (about 10 minutes) there's Hullabaloo in Deptford just off the high street.
There is a nice vegan crumble place called Crumble Mania on New Cross Road if you just want sweet stuff.
If Uncle Winkle is open when you're there they do decent vegan takeaway chinese options according to my mate (can sit down too).
Other than that though it's just look at the pubs in the area to see if any take your fancy unfortunately, most of them have a Vegan option I think.