Aldi's actually sounds OK to me. I wonder whether it makes a difference whether the word ends in a vowel or a consonant (I'm classing Marks and Spencer as vowel-final since most dialects wouldn't pronounce the -r)... Also, Aldi is especially s-able for me because I come from an area where *lots* of things get hypocoristics in -ees/-ies (cf. even in Cambridge 'Gardies').

To try to explain the exception to my final vowel rule (Ocado), I'm going to class the 'shop final s' as being phrased in the same way as a person's house ("I'm going to Naath's" or "The party is at Naath's"), which might respond to thinking of shops as physical spaces you can visit. So Ocado doesn't get final -s treatment because you can't visit it.

(This is only for shops, I'm not trying to explain Northfields type final s this way)