Here Geocoder inaccuracies when requesting co-ordinates for a postcode - here-api

Question

When sending city, postcode, country code in a structured query to the API, the results seem to be way off what is actually required.
Example #1 - City, Postcode, Country (removed API Key)
https://geocode.search.hereapi.com/v1/geocode?apiKey=XXXXX&qq=city=OXFORD;postalCode=OX2+0ES;country=GBR
This API call returns a result for postalCode OX1 3 which is not what I am looking for.
{
"title": "Oxford, England",
"id": "here:cm:namedplace:20338152",
"resultType": "locality",
"localityType": "city",
"address": {
"label": "Oxford, England",
"countryCode": "GBR",
"countryName": "England",
"countyCode": "OXF",
"county": "Oxfordshire",
"city": "Oxford",
"postalCode": "OX1 3"
},
"position": {
"lat": 51.75629,
"lng": -1.25951
},
Example #2 - Postcode, Country (removed API Key)
https://geocode.search.hereapi.com/v1/geocode?apiKey=XXXXX&qq=postalCode=OX2+0ES;country=GBR
This call returns the postcode OX2 0, which is closer to what I searched for, but still not accurate enough?
{
"title": "OX2 0, Oxford, England",
"id": "here:cm:namedplace:22218302",
"resultType": "locality",
"localityType": "postalCode",
"address": {
"label": "OX2 0, Oxford, England",
"countryCode": "GBR",
"countryName": "England",
"countyCode": "OXF",
"county": "Oxfordshire",
"city": "Oxford",
"postalCode": "OX2 0"
},
"position": {
"lat": 51.76224,
"lng": -1.27976
},
In some cases I have found while testing, is that the difference between the co-ordindates for the returned partial postcode and the full postcode is >= 8 miles out.
The question is, why when you attempt to be more accurate (including city) the response is inaccurate?
Also, if you are sending a full UK postcode to the Geocoder, why does it only resolve to part of the postcode? Surely if you send a full postcode, it should match?
Or, perhaps I need to use a different API. I did see another question with a similar issue that mentions Places API. Should this be used instead?