Bingo! That's brill @graz, thanks
EXECUTE AS LOGIN = 'sa';
RESTORE DATABASE MyDatabaseName
FROM DISK = 'X:\Path\MyDatabaseName_20150823_040100_Full.BAK'
WITH
REPLACE, -- (Restored to a name that didn't already exist)
NORECOVERY,
STATS = 10,
MOVE 'MyDatabaseName_data' TO 'E:\Path\MyDatabaseName.mdf',
MOVE 'MyDatabaseName_log' TO 'F:\Path\MyDatabaseName.ldf';
RESTORE DATABASE MyDatabaseName WITH RECOVERY;
SELECT [Owner name] = SUSER_SNAME(owner_sid)
, [Database name] = [name]
FROM sys.databases AS D
WHERE D.name = 'MyDatabaseName'
shows that the database is owned by "sa"