It's really hard to find fresh new vegan spots working in the West end every day but I recently found this little gem of a cafe 'VIETCAFE' on Haymarket which offers some lovely vegan options. I had the 'Goi Chay' aka summer rolls which had tofu, rice vermicelli, shredded pickles & herbed salad inside. I also had their 'Dau Phu Rang Muoi' which is lightly fried tofu served with a hoisin sauce.
I definitely recommend it if you're in the area and looking for a quick light bite to eat.
The staff are super lovely and the service was the quickest I've ever experienced lol.