Autofill Upwards With Reference to Adjacent Column

Please see test file with position numbers in column c.
The last position number in each range has a city stated in column b
I want to autofill upwards in column b the city name until position one for each range.

So on the attached file for example Manchester would autofill two above, London three above, Cardiff six above and Bristol five above.

My spreadhseet is far bigger. The attached example is just an extract.

Thanks for your help.