Woocommerce – Payment method doesn’t appear immediately on checkout page

Hello,
I have just installed a woo commerce payment system on my site https://www.siwmquest.uk.com. I am having a problem as at checkout stage (https://swimquest.uk.com/checkout/) the options to pay do not appear. Once you have chosen whether to pay deposit or full price – and click ‘place order’ the site comes up with error ‘invalid payment method’ message and then throws up the payment options (worldpay, BACS or cheque)

This isn’t a great user experience. Can someone advise?

Thanks,

Alice

https://www.ads-software.com/plugins/woocommerce/