Real answers, with receipts.

Garden roses, spray roses, delphiniums and dahlias. The first three suit your 10 July date: garden roses and delphiniums peak from mid-May, and spray roses are around all year. The dahlias come later, from mid-August, so a florist would swap those for July.

It matters, but not the way you are imagining: it changes how the photos look, not whether they are good. Simon Biffen calls the weather the biggest thing on the day and the one nobody controls, and thinks that is no bad thing.

Buttercream holds up in July. The worry usually comes from cakes sitting out all day, not from the buttercream itself. For a 10 July date it would travel chilled, go up close to the cutting, and stay out of direct sun.

It varies by stylist, but the usual shape is you first, most of the way, then the wedding party, then back to you at the end for face-framing. Hollywood waves get brushed out last, so they have the longest time to set.

They are for your partner, not the room. You will be facing each other, so as long as they can hear you, that is enough. Laura Crockett writes them with each partner separately, then reads both side by side so they match in length and in tone.

Take one finished invitation to the post office and have it weighed before you buy a single stamp. A standard letter allows 100g and 5mm of depth, and a suite with two cards, a liner and a ribbon passes that quickly.