From the i-resign link
Actually, you will not be dismissed at all, and this is an important distinction. What will happen is that you will have your contracts terminated, with notice, and will be offered a new contract to run, with continuous service intact, from the end of the termianted contract. If you fail to accept the new contract, in law, you will be deemed to have resigned.
The reason this distinction is important is that you will be unable to claim unfair dismissal - you will have to claim constructive unfair dismissal, and the difference is huge. Cutting to the chase, constructive unfair dismissal means that the burden of proof shifts from the employer to you, and very, very few cases of constructibe unfair dismissal are ever upheld. It is a claim that I would seldom recommend anyone trying without specific legal advice throughout, including before resignation, and even then, I would caution that the chances of winning are so slim as to be negligible.