Hello, I see you have worked there for 16 years so I will explain your legal rights in this situation. Assuming you are an employee, rather than self employed, the law says that if an employee has been continuously employed with their employer for at least 2 years they will be protected against unfair dismissal. This means that to fairly dismiss them their employer has to show that there was a potentially fair reason for dismissal and that a fair dismissal procedure was followed.
According to the Employment Rights Act 1996 there are five separate reasons that an employer could use to show that a dismissal was fair: conduct, capability, redundancy, illegality or some other substantial reason (SOSR). The employer will not only need to show that the dismissal was for one of those reasons, but also justify that it was appropriate and reasonable to use in the circumstances. In addition, they need to ensure that a fair dismissal procedure was followed and this would depend on which of the above reasons they used to dismiss.
So the employer cannot just find a replacement for you and tell you that you are now being dismissed simply because they have a replacement. This will most likely make the dismissal unfair and you would be able to challenge it further, such as by making an unfair dismissal claim in the employment tribunal.
This is your basic legal position. I have more detailed advice for you in terms of the steps you need to follow now, which I wish to discuss so please take a second to leave a positive rating for the service so far (by selecting 3, 4 or 5 stars) and I can continue with that and answer any further questions you may have. Don’t worry, there is no extra cost and leaving a rating will not close the question and we can continue this discussion. Thank you