Go on google and search for "employment lawyer near me". That will find you a decent employment lawyer.
Then you can have a talk with your managing director. You can tell him that you didn't expect the company in a shoddy way like that - the fact alone that you are aware that he is acting in a despicable way might change his mind. You can tell him that what he is doing is retaliatory, and any bigger company would have guidelines that forbid any retaliatory action in such cases. And finally you tell him that you talked to an employment lawyer (using one of the names that google showed you) and they would be willing to take your case if you are laid off.
PS. It is quite beyond me how people like Moo think that finding the name of a lawyer and even asking them if they would want to represent you would end up in thousands of pounds in cost. Fact is that companies hate litigation. Fact is that there is often someone above a managing director which will tell the managing director off if there is any litigation. So very often not the threat, but the hint, that litigation is possible, will work. And a single letter from an employment lawyer will make money companies cave in.