Using Miles to Upgrade

Hello everyone,
This is my first post, I'm new to V-Flyer.
My wife and I hope to use our miles to upgrade from Economy to Upper Class return, London-Miami, next April last two weeks afetr Easter holidays (dates flexible), fares not available yet on Virgin website(too far away).
We will have the 50,000 miles each for the upgrade, but what I would like to know is what is the cheapest qualifying fare L code? or similar in Economy likely to cost? Anyone have a ball-park figure? If we have to pay full Y fare then it's a non-starter.
Also would it be best to book as soon as the flights open or wait a while?
Hope some of you savvy regular V-flyers can help.

Welcome to v-flyer .
Like you said it's too early to get an exact price but you can get an idea by looking for an L fare for earlier for next March (but this may not be exact obviously).
Be warned, L fares can be significantly more expensive than O, X etc fares.
If you enter the VS website and log into flying club and then use the upgrade/companion option on the left hand side you can select an L fare. Don't forget there will be extra fees and charges to pay as well for a G. MIA does have some reward avaiability but in my experience it's not great. No point booking an L fare unless the G reward seats are there first.
Hope this helps .
DL

To give you an idea, a random date in March (10.3.13-24.3.13) for an L fare is showing as £864.49 (the cheapest L flights in March are showing as £829.49). Extra fees would be additional to the base fare.
Good luck .
DL

Hi,

I am trying to do the very same thing only for mid March these fares are just becoming available, at the moment the L fare is coming out at £824.49p for mid week plus fees which i reckon come to about £148 ish making £972 for the G.

Its best to book as soon as you get availability as they are changing like crazy all the time. Good hunting. Linda

Thanks all so much for taking the time and effort to reply, much appreciated.