Sorry for the late reply. Went away for few weeks. Right, I did manage to get it to work at the end. The key was to store retrieved attributes in an array and then add the array to listviewitem then add to control.

string[] columns = new string[] { i.Attributes["name"].ToString(), role.Name, i.Attributes["address1_city"].ToString(), i.Attributes["address1_postalcode"].ToString() };
                    ListViewItem item = new ListViewItem(columns);
                    this.CompanyList1.Items.Add(item);

Full Code:

 public void PopulateListView(DataCollection<Entity> items)
        {
            #region Set ListView

            ColumnHeader header1, header2, header3, header4;
            header1 = new ColumnHeader();
            header2 = new ColumnHeader();
            header3 = new ColumnHeader();
            header4 = new ColumnHeader();

            header1.Text = "Company Name";
            header1.TextAlign = HorizontalAlignment.Left;
            header1.Width = 100;

            header2.TextAlign = HorizontalAlignment.Left;
            header2.Text = "Primary Role";
            header2.Width = 100;

            header3.Text = "City";
            header3.TextAlign = HorizontalAlignment.Left;
            header3.Width = 100;

            header4.TextAlign = HorizontalAlignment.Left;
            header4.Text = "Postal Code";
            header4.Width = 100;

            CompanyList1.Columns.Add(header1);
            CompanyList1.Columns.Add(header2);
            CompanyList1.Columns.Add(header3);
            CompanyList1.Columns.Add(header4);


            CompanyList1.View = View.Details;
            #endregion

            foreach (Entity i in items)
            {
                if (i.Attributes.Contains("new_primaryroleid") && i.Attributes.Contains("address1_city") && i.Attributes.Contains("address1_postalcode"))
                {
                    EntityReference role = (EntityReference)i.Attributes["new_primaryroleid"];
                string[] columns = new string[] { i.Attributes["name"].ToString(), role.Name, i.Attributes["address1_city"].ToString(), i.Attributes["address1_postalcode"].ToString() };
                    ListViewItem item = new ListViewItem(columns);
                    this.CompanyList1.Items.Add(item);
                }

                if (i.Attributes.Contains("new_primaryroleid") && !i.Attributes.Contains("address1_city") && !i.Attributes.Contains("address1_postalcode"))
                {
                    EntityReference role = (EntityReference)i.Attributes["new_primaryroleid"];
                    string[] columns = new string[] { i.Attributes["name"].ToString(), role.Name };
                    ListViewItem item = new ListViewItem(columns);
                    this.CompanyList1.Items.Add(item);
                }

                if (!i.Attributes.Contains("new_primaryroleid") && !i.Attributes.Contains("address1_city") && !i.Attributes.Contains("address1_postalcode"))
                {
                    string[] columns = new string[] { i.Attributes["name"].ToString() };
                    ListViewItem item = new ListViewItem(columns);
                    this.CompanyList1.Items.Add(item);
                }
            }

        }