it's possible to improve the performance of the first query (qroverlapping) :
SELECT T.Id, T.surName, T.commDate, T.ceaseDate
FROM overlapping AS T, overlapping AS T2
WHERE (T.commDate<=[t2].[ceaseDate] AND T.ceaseDate>=[t2].[commdate] AND T.ID<>[T2].[ID])
GROUP BY T.Id, T.surName...