There is a M&S (and a British Home Stores I think) in Sliema.

For linen your best bet might be the markets. There are several around Malta. I think there might be a fairly large supermarket/shopping centre in Sliema also. Valetta and Sliema both have a good amount of shops.

Pippa

M&S

Marks & Spencer
The Strand Sliema
Malta
Tel: +356 21 331745

Marks & Spencer
Palace Square
Valletta
Malta
Tel: +356 21 220614

Marks & Spencer
Level 0, R3
Bay Street Tourist Complex
Bay Street
St. Julians
Tel: +356 21 37920401

(and yes, it is cold today !)

Hi Susan welcome to the island.
Yes, M&S on the Sliema ferries seafront and also in Valletta, walk all the way down the main Republic Street and turn left at the Palace. They also have a small food section at both stores. There are also BHS near the Sliema M&S and in Merchants Street Valletta (near the market)
Best place for household linens is JB Department stores at Lija.
There are a lot of electrical shops, the best value seem to be Mambra at Luqa, I have bought a lot of stuff from them and if something went wrong have never had any trouble with getting it replaced or fixed on the spot while I waited.
Good supermarkets near you are the Park Towers on the St Julians seafront for value, or the Arkadia at Portomaso if you need something out of the ordinary. Between the St Julians McDonalds and Police Station there's a Giormina bread and cake shop that also stock a limited range of groceries, they open 7 days a week until quite late in the evening, handy in case you run out of something.
Let me know if you need anything, and best of luck.

Sorry Mark posted as I was typing
He has gone one better and given you the full addresses/phone numbers!
The Bay Street M&S is a food/wine store only, the other two have clothes etc.
Bay Street is a good place to shop, there's also a play area for the kids

Hi Ingliza

thats a good answer - agree with all your recommendations