Hi all,

I've never used business class (simply never have enough money or avios) but currently have 25000 Avios and was thinking of booking the following (if possible).

I would like to fly to New York in Economy (during the day, so perfectly fine with me), but return overnight in business class (only way I would not got crazy on an overnight flight).

I've found very cheap cash deals as follows:
OUTBOUND to NYC: Economy ticket (no need to upgrade, happy with it)
RETURN to LON: Premium Economy (WTP) ticket found for very cheap price (about £100 above WT) - this is the leg I want to upgrade to business (CW)

I tried booking the above in one go using the "buy in cash, upgrade using Avios)" section of the BA website. I find it totally confusing, the price shown seemed ridiculous (not even sure it is what I wanted) and, thinking about it, I'm not even sure I could book the above ticket mix (whilst upgrading only one leg) using this method?

Would it make more sense to just book the cash tickets first (i.e. one economy outbound leg, one WTP return leg) and then call or use manage my booking to upgrade?

I will need around 20000 avios, is that correct?
Does anyone know approx. how much additional cash I need for taxes, etc (given that I am upgrading a WTP ticket to CW)? less than £100? £100-200? More than £200? More than £400?

I'm worried that I book my flights and then am told I cannot upgrade or that it is simply to expensive. I suppose I can still cancel the tickets within 24 hours for a full refund if I don't any upgrade opportunities?

To clarify, I have checked, for the WTP return leg I want to upgrade, that there is still reward availability for a CW seat for the same flight (there is).

Any advice would be appreciated as I find it all very confusing.

Best