Bidding for upgrade

Thinking of bidding for an upgrade from PE to UC on our JFK -LHR flight this Sept. I believe that you are informed a couple of days before so does this mean that you are likely to be assigned seats that are not so good ie next to the toilet or the bar. Anyone had a successful bid and still been able to get good seats. We will be at JFK nearly all day so use of the clubhouse would be good.
Thanks for your views/ experience
Michael

You are not usually pre-assigned a seat. You need to log in and select when your bid is successful. I have been successful a few times on bidding but generally been declined only to be able to use miles at check in - which has cost me a lot less than I offered.