I’ve eaten at a few branches of Leon, including this one and the one in Brighton and Heathrow successfully as a Coeliac with a dairy allergy. I find the staff extremely knowledgeable about allergies and I’ve never had a reaction from eating there. The gluten free chicken nuggets and vegan Aioli are so good! As are many of the curry/rice boxes. Very good fast food at decent prices for London, plus the children enjoy it too.