Not necessarily correct.
If the tenant is in a fixed term the first notice is not necessary, just the 14 day arrears followed swiftly by a Notice of Termination giving 28 days notice.
The first notice only applies where there is a Part 4 tenancy only. This came about by a poorly worded law where, with a Part 4 tenancy, the first notice was in addition to the other two notices.
However, it should be no problem to serve the first notice even where there is a fixed term in existence. It can be followed by the 14 day notice in another day or two.