Many thanks for your patience, I am pleased to be able to continue assisting with your query now. First of all, I am sorry to hear about the issues you have experienced in your situation.
I appreciate that the employer initially gave you the wrong notice period but that does not mean that once they have mentioned it there is no going back. If it was clearly an error and it was corrected without unreasonable delay, they will be able to do this and not have to honour it. Mistakes happen, it is human nature and just because someone has made a mistake, it does not mean that there is no way to go back on it and legally you should be allowed to take advantage of an obvious error.
In your case the error was identified relatively quickly and it is not like they allowed you to work for 32 months and only then realised it and try to go back on it, which would be too late. On that basis, you do not really have any legal grounds to force them to still give you 2 months notice, if that s not what you were contractually entitled to in the first place. There is nothing stopping you from negotiating with them but bear in mind what your legal position is, which will determine how much you ush them or ho far you go with it.
I appreciate this may not be the answer you were hoping for but it is the legal position and all I can tell you is what the law says. I do hope that it at least explains where you stand and I will be happy to clarify anything for you in relation to it. For now, thank you for using our service.