Entity Framework, Code First, Update "one to many" relationship with independent associations

It took me way too long to find a solution to the scenario described below. What should seemingly be a simple affair proved to be rather difficult. The question is:

Using Entity Framework 4.1 (Code First approach) and "Independent associations" how do I assign a different end to an existing "many to one" relationship in a "detached" scenario ( Asp.Net in my case).

The model:

I realize that using ForeignKey relationships instead of Independent Associations would have been an option, but it was my preference to not have a ForeignKey implementation in my Pocos.

A Customer has one or more Targets:

    public class Customer:Person
{
    public string Number { get; set; }
    public string NameContactPerson { get; set; }
    private ICollection<Target> _targets;

    // Independent Association
    public virtual ICollection<Target> Targets
    {
        get { return _targets ?? (_targets = new Collection<Target>()); }
        set { _targets = value; }
    }
}

A Target has one Customer:

    public class Target:EntityBase
{
    public string Name { get; set; }
    public string Description { get; set; }
    public string Note { get; set; }
    public virtual Address Address { get; set; }
    public virtual Customer Customer { get; set; }
}

Customer derives from a Person class:

    public class Person:EntityBase
{        
    public string Salutation { get; set; }
    public string Title { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set  ; }        
    public string Telephone1 { get; set; }
    public string Telephone2 { get; set; }
    public string Email { get; set; }        

    public virtual Address Address { get; set; }
}

EntityBase class provides some common properties:

    public abstract class EntityBase : INotifyPropertyChanged
{