Thanks so much for the response. I did try switching to a default theme but it made no difference to the layout.
I have added the following to the additional CSS which has now managed to line up most of the content.
.woocommerce .col-1, .woocommerce .col-2{
max-width: 100%;
}
.form-row {
flex-direction: column;
}
.woocommerce-checkout .form-row {
display: block;
}
.woocommerce .form-row {
display: block;
}
