Upgrades and Tier points

I am booked LHR to IAD on Sat with a Y ticket. I have just realised as I am only 8 points from Au that if I was PE one way and UC the other leg I would make Au. So the questions are:
If tried for an upgrade at the airport would I get the tier points?
If I upgraded with miles I wouldn't get the tier points?
I suppose the other question is it worth dipping into my own pocket to reach Au?
I see from searching the forums it may be cheaper to do the upgrade at the airport. I know it is all down to availability/numbers on the day but wanted to be prepared. I usually pay for the extra leg room seats (grudgingly) so that is a percentage reduction.
Do I ask for the price of the upgrade at the check-in desk or the ticket desk?
Thanks
Chris
If tried for an upgrade at the airport would I get the tier points?
If I upgraded with miles I wouldn't get the tier points?
I suppose the other question is it worth dipping into my own pocket to reach Au?
I see from searching the forums it may be cheaper to do the upgrade at the airport. I know it is all down to availability/numbers on the day but wanted to be prepared. I usually pay for the extra leg room seats (grudgingly) so that is a percentage reduction.
Do I ask for the price of the upgrade at the check-in desk or the ticket desk?
Thanks
Chris