[susan53]

Don't worry - you're not the only one. It's very common to use the singular is with a plural complement in informal speech. It happens a lot with There's, but also in expressions like How's things?

No, it's not strictly "grammatical". But it is normal usage.

There is/are does have two meanings : a quantifying use - There are four people in the room, There's a lot of traffic today - and a demonstrative use There's John! There are the people I was telling you about. To distinguish between them ask yourself if you could replace There with Here and change the sentence into the past. if the answers are Yes/No respectively, it's the demonstrative use - as in your sentence. But I don't think it affects the there's + plural problem.