Q: I never received my complimentary 20GB storage!?  how can I rectify this oversight?

Your free iCloud account includes 5GB of storage.  If you wish to have more, you need to purchase it.

http://www.apple.com/icloud/features/

and http://support.apple.com/kb/ht4874

The additional storage beyond 5 GB was not an indefinite gift, it will have expired by now.

Full members of MobileMe who migrated to iCloud got complimentary extra storage until September 2013; but this does not apply to Family Pack sub-account members.

If you had a full or master account and have not got the extra storage you will need to contact iTunes Support (but remember that it will disappear again in September unless you pay to continue it).

If you currently happen to have AppleCare, either because you recently bought Apple hardware or have paid to extend the inititial period, you can contact them here:

http://www.apple.com/support/icloud/contact/

You will need the serial number of the covered hardware.

If you are not covered by AppleCare, then - in common with other free email services - there is no free support and you may be asked to pay a fee - in this instance you should be able to persuade them that it's their problem and you shouldn't be charged.

Was that September for everyone Roger, I had 2 accounts both with a complimentary 45 or 50 GB (can't remember which), both have expired.

When the migration originally took place, migratees (from the full account) got the complimentary upgrade until September 2012. However Apple failed to turn it off at that point, and after a couple of weeks announced that it would be extended to 2013.

Their documentation on it is here:  http://support.apple.com/kb/HT5527

It says:

As a thank you to our former MobileMe members who moved to iCloud, we have extended the complimentary storage upgrade they received until September 30, 2013. This extension applies to accounts moved to iCloud between October 12th, 2011 and August 1st, 2012.

and

We will continue to provide you with this additional storage until September 30, 2013, or until you choose to upgrade your iCloud storage plan....If you need to upgrade your storage to a larger amount, you can purchase one of our standard storage upgrade plans at the regular price.  Please note that when you purchase a new storage upgrade, it will replace your complimentary storage plan. If you cancel the upgrade at a later date, you will return to the standard free 5GB storage plan and will no longer have access to your complimentary storage upgrade.

Thanks Roger, I'll double check that when I'm next in the office, but I'm pretty sure they are both back to 5 GB. My own personal space was new (from my existing ID from iTunes) it's always been 5 GB.