I would begin by getting the marriage certificate of Thomas & Jane James, this will tell you where they were both born. Most Likely in the UK Nicholls is most likely from Cornwall. You can get this certificate from www.justice.vic.gov.au
for a small fee (you need a credit card) you can download it instantly.
If you already know who his parents were from his death entry, let me know and I will try and find where he is from.
They do not seem to be buried in Geelong.. but stephen James is buried with possibly his son and Edith is buried with possibly another son.
Do you know when Thomas & Jane died.