Microwave for Charity, not for food (Swadlincote)

Need a working microwave for my not for profit art and craft group who have mental and physical health issues. An old type one with dials, a stores "own brand" would be best and preferably 800w or higher. Not Samsung, Daewoo or Sharp as these won't work. It's for a small microwave kiln as I want to do some fused glass jewellery with them, so doesn't have to be in perfect condition.