The show must go on is a popular expression from show business. It might be said when unexpected problems arise with any planned event.
You have the floor is a way of handing over an audience by addressing the next speaker directly.
The floor is yours is an alternative way of wording the above sentence.
The floor is open invites members of the audience to speak. If they become embarrassed, they might wish the ground would open up and swallow them.
Take centre stage is to be in the middle, where the main character should be. If a minor player takes this position in life or in the theatre they may have upstaged someone with a better claim.
Spread the word means tell other people (as appropriate).
Noise it abroad is perhaps less discriminating.
Left, right and centre is every direction.
A circus ring is a different space for performers.
Playing with fire is knowingly doing something with undesirable consequences.
To have something under your belt is often applied to an achievement or qualification.
Who’s she, when she’s at home? is asked about someone the speaker has not heard of. It is a sort of joke, as any person of integrity should have the same identity at home or anywhere else!
All over the shop is not neat and tidy or calm and collected. The shop in question could be a store or a workshop.
Loom large means preoccupy if it is an idea, which is looming large. Loom here is not a weaving loom, but the verb meaning to appear vaguely and often magnified. (I consulted the Concise Oxford Dictionary for part of this definition.)
Plumb in the middle is in the exact centre. Plumb is derived from the Latin for lead, plumbus. A lead weight is tied to string, making a plumb-line, which hangs vertically. It is used by builders and decorators to check that a vertical line is true.
One of the Old Testament prophets used it as a description of God’s requirements of him as a prophet. Amos 7:7-9