Everywhere listed is after security so if you’re flying from another terminal check out the guide to Heathrow's restaurants, cafes and bars on their website.
Wagamama - I've been a bit of a Wagamama critic in the past, in Brighton there are a tonne of vegan options so this chain has always seemed a bit lacking but the airport location somehow elevates their options from a meh to a yay in my mind. Am I still irritated that there’s milk in the pickles and that the soba noodles aren’t vegan? Sure, but I can appreciate a bowl of Saien Soba with udon, their Yasai Cha Han, hold the egg, and their breakfast options which include Breakfast Yasai Yaki Soba, switch the soba noodles for rice noodles, and baked beans on sourdough toast.
The breakfast menu also includes the Asa Gohan - sticky white rice, miso soup and pickles which may or may not contain milk. Wagamama have said on their Facebook page that their pickles may contain milk but it's unclear whether this is a traces of thing and they haven't responded to my e-mail so I can't confirm either way.
Pret - Pret have a surprising ammount of vegan options these days and they all hover on the healthy side of the spectrum. Their menu / vegan options change pretty regularly but there's usually at least one vegan sandwich or wrap available as well as breakfast options like porridge and . I spotted the Super Greens & Reds Sandwich as well as some juices, fruit pots and snacks including Crisped Kale and Sweet & Salty Popcorn.
Giraffe - Giraffe, like Wagamama, is somewhere you can stop for a sit down meal before your flight. Their menu changes pretty regularly but there website has a super helpful tool to help you suss out what's vegan as their options aren't marked on the menu. They don't serve their full menu at the airport but right now you can choose from a mix of sides and small plates including sweet potato fries, a hummus sharing platter or some edamame.
If you’re flying in Club World or are a BA Silver or Gold Card holder you can chill out in the BA Galleries Lounge. There are two of these and they're located at the North and South ends of the terminal. Not only do they have free fruit and water (best!) they also have both lightly salted and sweet chilli kettle chips and soy milk is avaiable on request.
Clearly labelled vegan the jar of biscuits is located in a slightly gloomy corner but one worth venturing over to. These were definitely a welcome addidion to my usual fruit, crisps, water game.
If you don't have lounge access don't fret, you can still access wifi at Heathrow. If you join the network all you need to do to access four hours free wifi is to sign in with your name, e-mail address and flight number.