Switching sidebars in theme layouts

Hi

This is for Cazuela v. 1.0.2.1

On my main page, I have two sidebars (1 & 2) and the content in the centre –

https://tutors-in-bristol.co.uk/

When I switch to a single sidebar on some of my ancillary pages,the page only displays sidebar 1 (irrespective of whether I chose the right or left sidebar display on theme layout) – see below:

https://tutors-in-bristol.co.uk/contact-me/

How do I change settings so that when I switch to single sidebar view, it display only sidebar 2, and not sidebar 1?

Thanks