Using Miles for UC or Upgrade Ecom ticket

I have booked two tickets to SFO using miles this October. I have read lots of posts where it seems to be better to buy ecom tickets and upgrade. Does anyone know if that would be better? They haven't taken the money for the tickets yet (tax etc) would they allow me to change or would that incur a loss of miles?

Thanks

According to VA terms and conditions, 4.2.1 states that changes may be made to date of travel, route and class at a fee of £25, however it would appear that if you cancel you will only receive 75% of the miles back and incur £25 cancellation fee.

I would phone FC and chat to them about.

[preiffer]

Advantages :
It'll get you at least another 10,716 miles (as you'll earn on the revenue part of the ticket)
It could get you more, if you're Gold/Silver
It's 4 more tier points each
You'd use less miles (60K rather than 100K) per ticket

Disadvantages :
Cheapest L class ticket (you can't just upgrade any economy fare) is around £500 - so it'll cost you another grand. That's the minimum - it goes UP from that price.
As Andy says above, *technically* they could charge you a 25% mileage penalty on your existing booking...

... but personally, I'd doubt they will. [:I]

Thanks for your replies. I booked before the miles went up, so only used 80K for each ticket. It appears then that I would only save 20K and possibly nothing if they take 20K away for the change. I will ring them, but probably stick with what I have got.