I agree with the above, and make my usual point that the fear of being downgraded generally and vastly outpaces the actual risk. It is true, though, that having paid for seats makes it less likely to be downgraded. Those most at risk of downgrades are those not holding a seat when they show up at the airport, so those who don't / can't do OLCI are at risk. But even if we are in an oversold scenario you can't pro-actively call up and ask to be moved, BA will ring customers and ask them to consider a move in some cases, and very occasionally a Customer Guideline goes out, typically offering WTP passengers the option of going on other flights and being upgraded to CW.