Your umbrella employer has to keep you up-to-date with the terms and conditions of your employment when they change, even if it’s relatively small.
By law, all employers are required to inform employees of the exact terms of their employment. Many umbrella companies perform reviews from time to time, which can result in a few minor adjustments being made. Key items relating to your employment (such as how you are paid, how much you are paid, where you work etc) will generally remain unchanged.