Section 21 notice. When do I have to leave the flat?

I was served notice (section 21). My term fixed contact would end on 26th March. I received a notice to vacate the flat on 18th April (2-month notice). My contract says that I would have to serve a 2-month notice as well if I wanted to leave the flat. But the landlord served me notice. If I find another flat to move in before 18th April I could leave the flat? Or I would have to pay the rent until 18th April anyway?
Thank you

The usual amount of notice a tenant has to give is one month -equal to the rent period, so think you could argue this point as an unfair contract term. But notice from you may have to coincide with the rent dates, depending on what your tenancy agreement says.
So if your rent date is the 18th, then even with one month’s full notice, it would now mean the 18th April is the earliest you could stop paying rent.
If you have found somewhere to move to you could ask to go before then. I believe you and the landlord would have to sign a surrender of tenancy document.

Does your tenancy agreement say that it becomes a contractual periodic tenancy when the initial/fixed term expires? This could affect the answer to your question.

No. It doesn’t say that. And I paid my full tenancy in advance.

You would be able to leave on 26th march at end of your fixed term. There is no requirement for you to give notice. If you dont leave it will convert to a statotory periodic tenancy which will be based on your payment frequency but would end on 18th april when landlords notice expires.

It may be that the landlord is happy to end the tenancy early if you find a new place so worth asking them if they are willing to end the tenancy early once you find somewhere.

As Richard19 says, you can end the tenancy by leaving on the last day or before without notice, but your liability runs until the last day - 26 March. You cant serve a valid notice during the fixed term unless your tenancy agreement gives you that option. If you serve notice after the fixed term ends, it must be a minimum of 1 month expiring at the end of a tenancy period. The tenancy clause about serving 2 months notice would have no effect in a statutory periodic tenancy.

Thank you all for your help!