The most likely cause of a warning, possibly referencing *.timpani.co.uk, is if you've not uploaded an SSL certificate. We use shared infrastructure, to make getting a site working for you faster. Most end-users will never see this error page. It is relatively safe to go into advanced options, and accept this SSL certificate for your site. You will not see the warning anymore.
Alternatively, it may be worth getting an SSL certificate. You'll need to use a Certificate provider to get one. If your cert provider requires you to provide a "CSR", let us know and we can generate one for you.