Buying PE now, upgrading to UC later

I've been giving conflicting information by two VS reps over the phone, so I thought I'd turn to the trusty V-Flyer gang for a more accurate answer!

There's great prices on PE flights to London from the US in December, but I'd prefer to fly UC if I can snag a deal (as I did last year).

So, my question is: If I purchase the PE flights now, and at a later date VS offers great prices in UC, will I be charged a charged a change fee for upgrading to UC on the same flight? Or simply pay the difference in fares? Yesterday I was told I only pay the fare difference, as long as I remain on the same flight. Today a different VS rep told me that I would have to pay $275 to upgrade to UC, in addition to the fare difference. So which is correct?

Just the fare difference if upgrading

I have upgraded a couple of time and just paid the fare difference

Fare conditions for K say

Penalties
Changes any time charge usd 275.00 for reissue/revalidation. Child/infant discounts apply. Waived for illness or death of passenger or family member. Cancellations any time ticket is non-refundable in case of refund. Waived for illness or death of passenger or family member. Note - may be used as credit towards the purchase of a higher vs fare type with a penalty of usd 100 and collection of fare difference. may upgrade the entire journey to a higher cabin at no charge but any difference in fare must be collected. ----- the fare must be recalculated from the point of origin and any difference collected

Thanks, I had a feeling that was the case.

Penny: where on Virgin's website can I find that small print?

its in the fare conditions of the ticket when you select your flight, click the link under where the total flight price is shown

its in the fare conditions of the ticket when you select your flight, click the link under where the total flight price is shown

Got it! Can't believe I've never clicked on that link before. Thanks Penny!