Form 8822 Change of Address-Do we need to do?

While reading the instructions on form 4868 to get an extension to file (yes, I am running a bit late!), I came across something that said if my address has changed since my last tax return, I'd need to file form 8822 to indicate this change of address. 

Is this true? Since my last return was filed in the US and now I am filing in the UK, do I need to fill out 8822 BEFORE I can send in my forms, including 4868 to get the extension?

Thanks for any help with this.

The 8822 is usually filled in when you are moving to another IRS district (i.e., from filing at the Andover IRS office to the Austin one) or if you've got a refund which you haven't received yet and you want to make sure it isn't lost.  I don't know where you posted your returns in the past, but it's now Austin/Houston.  If you don't know either, you should fill it in and post it.

No rush to do this, no specific order (do a before b) to do this; it's all about letting the guys at the last office know you aren't ignoring your tax stuff.

Ta very much!