Hi @paul2009 – that's so helpful, thank you! Maybe not so helpful of Lodgify not to have identified/fixed this, since they claim to have easy integration with Squarespace.
Your code above has worked a treat. My remaining issue is that there is now a scroll bar along the bottom of the home page (https://www.stoerview.co.uk/home), which shows grey padding if you scroll right. This appeared when I added the initial bit of container code in the CSS, but didn't disappear when I removed it. It only affects /home, not the other pages. Have I messed something up when I initially added the wrong CSS code? Any advice appreciated.