I'm moving away from the area at the end of March and I want to give my current employer 2 months notice instead of the statutory 1 month. This is due to the fact that we are already one member of staff down in our office at the moment, and I want to give my employer enough time to get a replacement for me too. I get on very well with everyone in my office as well as my area manager and I really don't want to leave them in the lurch. I know my area manager would appreciate the extra time, but could the HR Department insist I only work 1 month notice?
Write down the possible advantages for you of giving two months notice instead of one month. You will find the list of possible advantages is absolutely empty.
And if you give two months notice, your employer can decide to give you the shortest legally possible notice, and you'll be out of money for some time.
Now in practice, it's none of your HR department's business to decide how long you are working there, except to check that whatever happens is perfectly legal (and isn't against the companie's interest). It would be your manager's decision primarily to say for how long they would like you to work there. Of course if your manager wants you to leave, that's it.
I know my area manager would appreciate the extra time, but could the HR Department insist I only work 1 month notice?
It's possible, but unlikely. HR seldom cares about such details. They will just want to know when is your last work day so that they can process all the relevant paperwork. And unless there is a corporate policy or law in play, HR will seldom go against the manager's wishes.
If you are confident that your boss will receive the news well and appreciate the extra notice, then go ahead and try for 2 months.
Just give them one month's notice. The notice periods are set by the company to give them enough time to get a replacement. It's not your fault if the company don't do it in that time frame.