Google basis (free) does not provide address verification (Geocoding) as there is no UK postcode license.
This means postcode searches are very in-accurate. The proximity search is very poor, even for town searches, often not recognising locations.
This is why Google have a premier and a enterprise solution which still is more expensive and not as good as business mapping specialists like bIng and Via Michelin who also have API's.
As a free lance developer, so serious business would use Google as the system is weak and really provides a watered down solution.