Hello Stuart Kennedy,

Apologies for replying late, we are not working on weekends. 

You should add this custom HTML to the page where you have Amelia shortcode: 

<style> 
#amelia-step-booking1 > div.am-select-service > form > div.el-form-item.am-select-employee-option > label, #amelia-step-booking1 > div.am-select-service > form > div.el-form-item.am-select-service-option.is-required > label
{font-weight: bold !important;}
</style>

You can also change /add some custom CSS inside the {} brackets, I put font-weight to bold, but you can change it to whatever you need. 

Hope this helps, 

If you have any further questions or concerns feel free to ask,