My name is ***** ***** I will try and help you today.
I am sorry you are experiencing this problem with your landlord.
A section 21 notice doesn't normally expire unless the landlord withdraws it.
Technically, it could be argued that by issuing a new notice they are withdrawing the previous one.
The first notice expires in October whereas one served now will also expire in October as all notices served from 1 June 2021 have to give 4 months notice.
Either way, you cannot be evicted without a court order and a warrant of execution with the bailiff that provides you with another two/three months.
This is especially so due to the backlog of cases caused by the coronavirus.
You also need to check that the section 21 notice is valid as you may be able to challenge it.
Was any deposit placed in an approved scheme?
Were you supplied with a Gas Safety Certificate and Energy Performance Certificate?
Were you provided with the Government's booklet on "How to Rent?"
If you want to instruct a solicitor to help call the Law Society on 0207(###) ###-####who can recommend local firms who can assist or call Shelter on 0808(###) ###-####who can provide advice.