OBACHAN'S SCRIBBLES

I was going to visit my parents’ house this weekend, but looks like I need to postpone the visit. Well, maybe it’s a good chance to stay in my apartment and re-start some things that I haven’t been doing since the beginning of the summer. Gee, now I think about it, I haven’t played the keyboard for a L O N G time…!! :O

One quick damn question about English grammar:
Talking about subject-verb agreement, is “a pair of” considered singular or plural? Do you say “A pair of shoes IS lost” or “A pair of shoes ARE lost?” A British guy and I got caught up in this question yesterday, and since we didn't have an access to the internet when we were talking about that, we had to sink in the deep mud for quite a while. (Of course I'm kidding.) :P

I always thought it was singular, but going through some grammar sites and forums on the net later, I found that it is treated as plural in certain situations. According to American Heritage Online, “A plural verb is used when the members are considered as individuals.” Is that so in British English, too?
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I guess I simplified the example a little too much. The actual sentence we were wondering about was more like this one:

A pair of zori, Japanese traditional sandals, is/are lost.

I thought that the inserted part wouldn’t make a difference and the verb would be singular because the subject of the sentence was still “a pair.”

I really want to know how it is in British English grammar, though. They seem to have a bit different idea about singular/plural issue, because most of British people I knew said "a number of people" is singular because there is "a" in front of "number of people."