"All my files (quotes, invoices etc) are stored on my home office PC. I want to be able to either access these files from my work PC and work on them remotely..."
Have a look at TeamViewer which will let you either access files on a remote computer or "remote control" it.
"...or be able to synchronise the two hard drives so that whatever i do at work will update the files at home and vice versa"
You can do this with Dropbox by putting all of the files you need to work on into the special Dropbox folder in the PC.
"I also would like to somehow sychronise my emails between the 2 PC's so I'm not missing replies etc when i work from a different workstation."
The best way to do this is to use IMAP protocol instead of POP3. With IMAP, all mail is stored on the provider's servers and your email programs (in as many computers as you want) synchronise with the IMAP server. You have access to all folders, including sent mail, from every computer that you have set up with your IMAP settings.