Lay vinyl flooring over self adhesive tiles?

Hi I'm going to have vinyl flooring fitted in our kitchen (3m x 5.6m). At the moment the visible areas have self adhesive tiles and under the dish washer and washing machine it is bear concrete. Some of the self adhesive tiles near the kitchen units are starting to come away. The vinyl is being fitted by the company supplying the vinyl but I was wondering how best to prepare the sub floor before they come to fit the vinyl.