Problem creating unique values to create a relationship

Hi

I'm trying to join two tables together through a relationship but am having trouble. 

My data is of a Building (type text) , which has Floors and Rooms which can both be a mix of text and number names (type any).  

In order to create a relationship based on the Room column, I attempted to create a unqiue values table by referencing the Room_Mapping table, removing all by columns apart from Room, and removing duplicates. 

However, when I try to join the two tables together based on the Room column, I keep getting the following message. 

I have a feeling that this error is coming because the data type is a mix of text and numbers that it is getting confused because when I go to look at the data in Data view, I can see that the data for Phase and Room fields have been converted to Text type.  

Please can any one help?  I have attached a link to the workbook and data in the link below.

Room_Mapping Data and PBI Workbook

Many thanks in advance.