Given the Covid situation and the longer notice required, you aren’t going to need to move any time in the near future.
It is up to you whether you allow viewings if the property or not.
Solicitors will advise the owner that it is always best for the tenant to be out before starting to market and unless the property is sold to another landlord with the tenant in situ who is going to stay, exchange cannot happen u til the tenant has vacated.
So, essentially you have some time to think this through and to see what works for you, rather than needing to be panicked and making choices you later regret.
How do you feel about moving on and looking for another property in perhaps a month or 3 months or 6 months? Which timescale is best for you? You don’t need to be considering getting out instantly. If you really want to hang on in there, you can refuse to leave and the legal proceedings will take ages, but you can do that if you want. Most people won’t do this but vacate at the end of the notice period given.
It is annoying for landlords when they can’t market their property as tenants are entitled to not allow viewings, however, landlords know that is the case and always need to really plan ahead with wanting to sell, and think about then their tenant will leave etc. Just deciding to sell and expecting to automatically market it immediately and that tenants will be gone speedily is unrealistic of a landlord and tenants are rightfully protected against landlords being able to just insist on these things.
What works for you Op? Have a think about it and then talk with the landlord, in full knowledge of the current notice periods required and your rights about viewings. The LL has rights and so do you. It should be possible to work together within these rights and find. Way forward.