In Tokyo, are most places closed for the whole of GW? Just Wed. - Fri? Not at all?

I haven't spent much time in Tokyo, but what kind of "places" are you wondering about?

Just places in general -- I assume banks are closed, but what about konbini, supermarkets, bookstores, Tsutaya, Shimachu homes, etc. Of course I know it depends on the business but I just wondered if there was a general pattern.

everything will be open except public offices (immigration etc).

Yeah, I'd figure pretty much what Nadiatims is saying. Though not technically public offices anymore, I believe post offices will also be closed all the week except Tuesday and Thursday. Some small mom & pop operations might be closed (small restaurants for example), but then most will probably be open to cash in on the holiday business. The post office has been stressing that their ATMs are going to be unavailable from the 3rd to the 5th and other places will probably be the same, so make sure by the 2nd that you have all the cash you're going to need.

Yeah, I'll do that (although 7-11 isn't that expensive if you forget). Thanks.

I know some of the larger corporate offices will be open - Mitsubishi for example. I totally forgot how ATMs in Japan had opening hours....