So I re-configured my tables and set out as follows, and linked them accordingly in their relationships.
Customer:CustomerID(PK)Suburb(FK).. details
SuburbuburbID(PK),Suburb,Code
Item:ItemID(PK),Title,PlatformID(FK),Quantity
Platform:PlatformID(PK),Platform,GenreID(FK)
Genre:GenreID(PK),Genre...