The employer has not actually dismissed you but you feel that you have been given no option but to leave. A claim for constructive dismissal can be brought against your employer if you believe staying with the employer is impossible.
In order to bring a successful claim for constructive dismissal there must be a fundamental breach of contract by the employer. You need to leave alleging constructive dismissal. Staying on in your job and working your notice may be inconsistent with the argument that you believe you have no option but to leave. Therefore if you are relying on a breach of contract, you must act promptly after that breach occurs.
If you are successful in claiming a constructive dismissal, potential claims for both wrongful and unfair dismissal may follow. If you are unsuccessful then you will be regarded simply as having resigned. If your employer does not have a fair reason for your dismissal, you may be able to bring a statutory claim for unfair dismissal.
Fair reasons the employer may use to dismiss someone include capability, misconduct or redundancy.