Many thanks for your patience. The main issue for you here is that if you have been continuously employed at you place of work for less than 2 years then your employment rights will unfortunately be somewhat limited. Most importantly, you will not be protected against unfair dismissal. This means that your employer can dismiss you for more or less any reason, and without following a fair procedure, as long as the decision is not based on a reason which makes a dismissal automatically unfair. These include:
· Discrimination due to a protected characteristic (i.e. because of gender, race, religion, age, disability, sexual orientation, etc.)
· Taking, or trying to take, leave for family reasons including pregnancy, maternity/paternity leave, parental leave, adoption leave or leave for dependants
However, if the dismissal had nothing to do with any of the above exceptions, you would not be able to challenge it. In that case your only protection would be if you were dismissed in breach of contract. That would usually happen if you were not paid any contractual notice period due to you (unless you were dismissed for gross misconduct, where no notice would be due). If you did not have a written contract in place you would be entitled to the minimum statutory notice period of 1 week. The employer would either have to allow you to work that notice period and pay you as normal, or they instead have to pay you in lieu of notice, where you are paid for the equivalent of the notice pay but your employment is terminated immediately.
So whether you disclosed the conviction or not, it makes no difference unfortunately and they can still dismiss you regardless, simply because you do not meet the minimum criteria to challenge them for unfair dismissal.
I appreciate this may not be the answer you were hoping for but it is the legal position and I hope that it at least clarifies where you stand?