Section 21 landlord kicked me out

Hi just looking for some advice my landlord gave me a section 21 just before Christmas I have been thier 3 years put new carpets down and decorated it nice thinking it was my home the landlord said he was moving back in as split from his wife handed the keys back in and the house back up for let for 25 pound extra I’m fuming the stress this has caused me I have 2 children the money I falked put just before Christmas to move should have been spent on my kids for Christmas was just wondering if I had a legal case can he do this thanks