Compare two tables with same structure, but differing membership numbers
That should give you what you want:

SELECT UT.Name, T1.*, T2.membership_no as 'Unmatching in membership_no Second table' 
FROM T1
INNER JOIN UT
ON T1.user_id = UT.user_id 
INNER JOIN T2
ON T1.user_id = T2.user_id and T1.membership_no != T2.membership_no