two years tenancy agreement with a six months break clause

[IWannaBeLikeYou]

Would this be realistic or does a six months break clause only apply to a one year contract?

I'm not entirely sure what you mean but any tenancy agreement for longer than 6 months can legally be broken with 2 months notice on either side once the initial 6 months have passed.

If it is still a Shorthold Assured Tenancy(England) the length is irrelevant after 6 months as standard notice applies (2 months on landlord side , one on tenant iirc).

We are about to renew the tenancy agreement and I was considering if it would be better to renew for two years, as it would save us from having to do the same next year.
I wanted to be sure that we can still get out of it after six months if it was the case.

That being said, would there be an advantage in having the tenancy agreement for more than one year?

You can fix the rent for the next two years if you do it now. Also you don't have to pay the agents' fees of a new tenancy this time next year too.

Think about whether you would prefer a "rolling break" or specific break dates. A rolling break could end the lease at any time after 6 months, on notice as Lizs says. This doesn't actually give you much security if you want to stay but the landlord wants to end the lease (most break rights are mutual). The specific dates could be months 6, 12 and 18 - but if you miss the date, you are stuck in the place for another 6 months. It's an expensive mistake to make.