Query Cache and keep alive are settings that you make on the server.
a google search for:
found this link:
I'm sure you can find other resources for info on the keep alive directive.
We don't offer support for server settings.
at the end of the day, these are tweaks that should be used if you site is not responding as quickly as you would like.
"We are totally new to virtual/dedicated servers and server management and, were it not for the fact that we need an SSL certificate on the domain, we wouldn't have bothered"
you don't need to have dedicated hosting for an SSL certificate. There are many sites that use shared hosting and SSL.