The reliable way to hire a tradesperson

Hi, I'm replacing an existing timber garage, 2.5m x 5.5m, with a new timber garage. The current garage foundations don't look very substantial, suspect it's just some form of hardcore around the perimeter, as it has a wooden floor and I can see there is soil underneath. Would a 100mm hardcore/100mm concrete trench around the edge of the building be ok for a foundation? How wide would the trench have to be? I want a wooden floor so don't see the point in a full concrete slab. It's not going to have cars in it, purely for storage etc. Thanks.

I have an indoor fireplace where a coal burning range used to be. Bricks are either Edwardian or Victorian. The fire itself is now no longer used but bricks are stained. Some sources suggest not using modern brick cleaners on heritage bricks but I’ve found others saying its possible if the product is diluted or if the brick surface is wetted well. I’ve tried to find products specifically for heritage bricks but not having any luck.

what is the amount of mix of vinegar and peppermint oil for killing spiders /