The server will be going down very soon so that techies can get into the hardware and install some new memory modules. The server was meant to have 4GB of memory as standard but has actually only been running on 2GB since it was installed due to a fault in one of the memory components.
Fingers crossed this is the cure to the recent site stability issues!
Update
The server is back up with the 4GB of memory now installed. It's possible further tweaking will be necessary but lets see how it goes.