So it's launched today when will the uk networks be able to sell it? Tomorrow ?

No one "knows" it's launched today...yet

Normally it's released a couple of weeks or so after the announcement

I think it will be tomorrow based on the fact leave is cancelled at all Apple stores this week and next. But just wait for the announcement, it's only hours away now.

According to the Guardian:

Secrecy surrounding Apple's announcement of its "iPhone 5" on Tuesday evening UK time is so strong that UK mobile networks admit even they do not know precisely what will be unveiled, and so may not even be able to give prices until Friday.

The article suggests that UK networks can't even begin negotiations with Apple until after the announcement, so if that's true we'll have to wait a while.