A good place to start is taking a look at the company's job postings. They may not be the most descriptive but there is enough information to give you a few areas to look into. For example, check out these jobs
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One listing is for a CyberCrime Senior Associate and the job description says malware forensics, network forensics, and memory analysis. The requirement section mentions the following tools encase, FTK, helix, Paraben, and live memory collection. I won't repeat the entire listing but there are some other tidbits in there as well.
If it were me, I would look closely at those postings and then start learning the processes & methodologies they are looking for.
Corey Harrell
"Journey Into Incident Response"
http//journeyintoir.blogspot.com
A) What 5 tools would you say are essential for an investigator at PwC?
Law book, paper, pen, calculator and excel
B) Are Linux and Mac forensics a big focus in there firm?
No clue, you have to ask them. As someone pointed out, check the job ads, its a great way of getting an inside view of an organisation.
C) What 3 books could you recommend reading to bring me up to speed with the industry?
None. Go to SANS and take the forensics courses there.
D) Can you recommend anything else I should do to aid my job chances and increase my knowledge?
Stop focusing on one corporation.
E) I enjoy writing, should I start a personal forensics blog? Post test scenarios I completed, how I completed them etc.
When you have something to contribute to the community, perhaps.