Anyway, I hunted around a bit and found a page in Google support which seems to provide instructions that would allow me to set the update to occur, say, once a day, which would be fine. https://support.google.com/installer/answer/147176?h...
Trouble is, it involves writing some instructions in Terminal and they seem to have missed a vital part. It says:
In reference to support.google.com/installer/answer/147176?hl=en-GB:To change how frequently Google Software Update checks for updates, execute the following in the Terminal application:
$ defaults write com.google.Keystone.Agent checkInterval
where is the elapsed time in seconds between update checks.
Can anyone tell me where I should insert the number of seconds?