How wide are dining carvers?

Most measure across the arms at about two inches wider than the standard side chairs. The seat depth also tends to increase slightly to balance the proportions. They slide under standard dining tables just fine. The arm height was planned with table clearance in mind.

I bought a set with mismatched drop-in seats, and I want to get them covered in new fabric. Do they need sending to a specialist?

Drop-in seats are simple frames. You can often recover them at home using a staple gun and standard upholstery fabric. Leave the old webbing intact if it holds firm. Take the old covers off first. Adding too many layers makes the seat block jam tight in the chair frame.

Can I mix wood types?

Blending different timbers around a table works well. A mahogany table handles oak or elm chairs without looking odd.

When you look at the back legs on these sets, some are straight but others flare out at the bottom. Was this just a fashion thing or did it have a purpose?

Splayed back legs do follow periodic fashions. The Regency period favoured a strong sabre sweep on dining seats. The main purpose remains structural. A flared leg pushes the centre of gravity backwards. It stops diners tipping the chair over when leaning away from the table.