Others will no doubt cite laws and rulings, but you do appear — at the minimum — to have a moral claim for a ‘like-for-like’ restitution, having regard to the market level of the original kitchen. It could get messy if you have recently lashed out on a major upgrade. There does seem to be a case for mediation, for your own protection, so that any payment from the sinking fund can be seen to have been determined objectively on the facts, and at arm’s length.