Styling checkboxes in Contact form 7

When customising the look of a checkbox using CSS, to be able to work the magic we first need to link an element (eg. label) to the checkbox.

<label for="toggle-1">Do Something</label>
<input type="checkbox" id="toggle-1">

However I am using Contact form 7 (wordpress plugin) and I cannot find where to add the id within the checkbox. If you specify an id in CF7 it adds it to the containing div (.wpcf7-form-control), and not the checkbox itself.

Therefore I can't get it working.

Am I missing something? is there another way to link the label and the checkbox?

Many thanks