1337 sistah answers rhetoric questions and solves insoluble puzzles! 
soy milk, products, etc - should be available in most large supermarkets, esp. places like Tesco, Auchan and Cora (more common than you'd think; available in most shopping malls, which, again, more common than you'd expect). So, if you're in the vicinity of a shopping mall, head on in and start hunting for either a "health food store" (you'll know 'em when you see 'em), a Tesco/Auchan, or one of the well-stocked drogeries/ parfumeries (DM's are usually better at soy products than most health food stores, don't ask me why), and you're set.
Depending on which part of the city you'll be exploring/staying in, fast food places can be a good source of a medium priced meal. Avoid any and all Chinese fast food places - this includes the stalls in the food courts of malls as well! - as they'll tell you whatever you want to hear about the food. ("You want no meat? I take out meat. Spring rolls have eggs? No, no eggs, no milk, no meat." - In reality, they're all not-vegan, as they use grease, fat and meat soup/gravy as base for most dishes, and eggs for the rest. The only thing safe is white rice, and a salad if you're feeling adventurous.) Most "gyros" places have excellent falafels, though; opt out of the gravy/sauces and you're safe. (Yes, even the hot - red - sauce; I mentioned the gravy part for a reason.) In other fast food places/food court stalls the names of the dishes are usually labeled in English as well, but just in case: around steamed vegetables (including potatoes with parsley) watch out for the term "vajas" (=> made with butter; vaj=butter). Oh, and don't get fooled if they say that the food is made with "plant (based) cheese" - the logic of kazein as a by-product of a cow's suffering is completely foreign to the general (Hungarian) public. There are no "vegan cheeses" in Hungary; tofu is tofu, anything else is the product of cow rape, one way or another. Oh, while at the food court topic - unless you luck out and find a "natúra/vega" stall (the absence of meat is a dead giveaway), anything breaded and fried has also been covered in eggs somewhere during the breading process. Yes, even the mushrooms. What else... well, pizza places are usually a lottery - they might make vegan pizza bread, and then again, they might not. Places that don't have a complete fast food look are usually more amenable to preparing you a vegan pizza.
Oh, bread and bakery products in Hungary: I have yet to find bread that looks homemade and doesn't have a list of additives as long as my arm. Even worse for freshly baked products; stick to stuff that has a products list, and either memorize basic stuff like 'tej', 'zsír', 'vaj', 'tojás' and 'tejsavó' or just 'savó' - the last two are whey (powder) - in Hungarian, or hope to find a product that has its ingredients list in English, which isn't that uncommon. (You could also polish up your knowledge of German not-vegan ingredients, as it may come in handy.) Most breads have whey powder in them (as do most veg-looking sweets of the chocolates and cookies type) so read the fine print carefully.
Also, scratch was Kee-lah said - most big name snacks (Lays, Chio's Chips/crisps, etc.) are also rich with whey powder, even the 'natur'/classic ones. Read the fine print carefully, or buy brands you know are safe. Nuts, raisins, dried fruits and such are usually safe, as they come from the same places UK gets them from, I'd wager (i.e. China, Middle East, South America, etc.). Canned goods the same; 'Bonduelle', a Hungarian brand, while pricier than the others, has excellent canned vegetables which are edible straight from the can. One of the Hungarian insta-foods is 'lecsó' which is basically plain tomato sauce with red or yellow pepper slices cooked together; it's cheap, comes in a (big glass) jar, and makes a good dip for salty junk food.
Last but not least, if you want to try and meet up in Bp, what dates are you going to be there, and whereabouts will you be staying?
That be all, I think.
Almost forgot: for veg restaurants I can check around, since as I don’t tend to eat out much, and most of the ones I know tend to get renamed and/or relocated about once a year. (Except the couple of ones which are macrobiotic “haven” for the in-crowd and cost a pretty penny, but might be worth for you to check out if you’d like a real eating out experience while in Bp.)
Byeee!
"Life is uncertain. Eat dessert first." -- Ernestine Ulmer
Activists are the engineers of the soul. That's why governments lock them up.
) but in unknown places i'll eat the first or worst vegan thing i can get my hands on. no matter what language i'm quite sure peanuts (worst case scenario) will always be vegan. and potato chips/crisps (ugh).
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