Sorted it, for anyone interested the following works for me :
Select Top 1000000 tblADusers.DisplayName,
tblADusers.Displayname,
tblADusers.Office,
tblADGroups.Name As 'Active Directory Group Name'
From tblADusers
Left Join tblADMembership On tblADMembership.ChildAdObjectID =
tblADusers.ADObjectID
Left Join tblADGroups On tblADMembership.ParentAdObjectID =
tblADGroups.ADObjectID
Where tblADGroups.Name Like 'YOUR-GROUP-NAME!'
Order By tblADusers.Name