when referring to company names...

when referring to company names (a company usually being made up of more tha one person) is it right to treat them as singular or pulral? For example: "Harrods are pleased to announce..." Harrods is pleased to announce..." "Tesco are delighted to say..." "Tesco is delighted to say..." I normally refer to them all as plurals as I feel it reads a lot better, but what is right?

[Anglika]

In neither case is it technically plural. It is possessive but has lost the apostrophe.

Harrod's
Tesco's
John Lewis's
Waitrose's

and so on.

[marilyn2]

Sorry, I think you have misunderstood the question. If I was saying: Tesco's new range, or Harrods' new collection, then I think the apostrophe placement is correct but, in the examples I gave previously, an apostrophe would not work...

[Anglika]

I did not misunderstand.

The companies are Harrod's [named after its founder Mr Harrod]; Selfridge's [named after its founder Mr Selfridge].

The apostrophe has been lost, so Harrods and Selfridges is how the companies concerned are now called and a singular verb is used. In a press release, both these will be Harrods is going to... / Selfridges has taken the ...

In the case of Tesco or Asda, I would expectTesco will be .... / Asda is going to ....; i.e without s and a singular verb.
If you have any problems or doubts, the first place to check is the company's own website, and follow what is done there.