That's not the case in London. The notice you need to give a tenant is specified by the lease agreement (general an Assured Shorthold Tenancy). It's usually specified as 6 months minimum, after which either tenant or landlord can give 1 month (or sometimes 2) months to end the lease.

If the tenant refuses to move out (despite the landlord serving notice correctly) you can usually get that resolved in 2-3 months at most: 1 month to get a court date, 1 month to give the tenant time to comply with what the court orders, and 1 month to get a bailiff to physically remove them (if it comes to that).

(Source: I'm from London, and I've signed several leases as both a landlord and as a tenant. I've once gone to court to evict a tenant who had stopped paying rent, and the matter was resolved in <2 months from first filling in the court paperwork)