It sounds like a problem of redirection URL.
Normally you should have this line:
<input type="hidden" name="return_url" value="<?php echo urlencode(base64_encode(urldecode($this->redirect_url)));?>"/>
near the end of the file "add_to_cart_listing" of the view "product" via the menu Display->Views.
If that's the case, change it to:
<input type="hidden" name="return_url" value="
www.britishfoodabroad.co.uk/index.php/pr...ts/product/listing"/
>
and that should solve the problem.
If you don't have it, please give the content of that file. And check that it's the latest version of the file (you can look at the header of the file at the top for the version number). If not, please delete the customization on the listing of views and try again.