Here’s a little advice for you, to make your lives more rewarding and mine less frustrating. It relates to how shop names should be said and written. Here goes.
Asda and Tesco are singular. There is never a need to saying you’re going to Asdas, unless you’re going to Asdas up and down the country in search for the last remaining Pokemon on Christmas Eve. If you need to pluralise Tesco in such a way, it’s Tescos.
McDonald’s and Sainsbury’s should both be written and said such. I went to McDonald’s. While this is a lie, it’s at least grammatically correct. In writing, avoid at all costs using these with a possessive apostrophe, as this is how wormholes are created. Talk of the profits that McDonald’s made, not of McDonald’s’ profits, or however it might be written.
Marks and Spencer doesn’t have an S at the end. Feel free to abbreviate to Markses, but only if you want to go to Hell.
That is all.