User Created Using Dacpac Cannot Log On

I have a Visual Studio 2013 SQL Database Project which creates a DACPAC file for deployment of the SQL database to SQL Server using the 'Deploy Data-tier Application...' option is

Solution 1:

So eventually I got to the bottom of this with a colleague's help, and the missing part was the following two lines after the CREATE USER ... statement:

GRANT CONNECT TO[MyLogin];
GO

Now the DACPAC correctly deploys the SQL database and applications can connect to the database using the created MyLogin user.