On further checking I can see that the calendar data file local.sqlite is in place within the profile structure. My question now is, how do I get Thunderbird to recognise the data file? I tried disabling Lightning and re-enabling however this did not work.

You'd have done better to restore your old profile, which is probably where your Tasks are stored.

http://kb.mozillazine.org/Recovering_a_profile_that_suddenly_disappeared

Also, you may be able to find your old profile and transplant that sql file into your new profile.

I don't use Tasks myself, but I do use an online calendar which stores my Events, and so they would be restored from their online location once Lightning has been re-connected to that online calendar. However I am not confident that the online sync I am using (CalDav with Google Calendar) can handle Tasks.

You can use a local ics file as a form of online calendar, but stored locally (and therefore privately) and this is useful if you want to share a calendar or use it on multiple instances of Thunderbird, e.g. a Windows /Linux dual-boot system. I use an ics file, stored on Dropbox, to make a calendar visible to any of my Windows and Linux computers.

Both of these ways of using an online calendar are handy in that when you do need to reinstall Thunderbird with a new profile, the data just magically re-appears once the accounts are set up, just as your messages do in an IMAP-connected account, where your messages are stored "in the cloud" on a mail server.

I tried deleting the profiles.ini file, creating a new one in the default location and copied the contents on the old profile to the newly created one. All old emails are displayed ok however the tasks tab is blank. It appears that the calendar data is not being picked up by Thunderbird/Lightning. I noticed a message that says "Thunderbird now contains calendaring functionality by integrating the Lightning extension" is anything different because of this? Clutching at straws maybe!!