Mapping UK Postcodes to Geographic boundaries for plotting

I have a dataframe with a (UK) postcode column, and a count column, e.g.

postcode  count
SW1W0NY   10
PO167GZ   22
GU167HF   15
L18JQ     38

I wish to create a heatmap of this data using folium, where the counts are aggregated as per larger (e.g. county-level) geographic polygons.

There are several online resources which map postcodes to lat/long, but is there any python library or resource which maps postcodes to larger UK geographic regions (e.g. county level)?

Solution

The Office of National Statistics has such mapping files:

from Post Code to LSOA
from LSOA to UTLA
and from UTLA to corresponding geometric boundary files (UTLA codes are equivalent to CTYUA codes)

Note that the mappings and codes are version/year specific, and may not be cross-compatible.