Row 75 Premium Economy Upper Deck

Was wondering if people could help me out here. We are travelling out to Antigua, Premium Economy, on the 21st January, but due to booking late, the only seats left for pre-booking are downstairs, row 82.
I presume, being an exit row that row 75 on the Upper Deck cannot be pre-booked, and was wondering what people think are the chances of getting this row at check in?
Would I need to unbook my seats on Row 82 (I would like two seats together so have pre-booked these for the time being), we are going to use the twilight check-in as it is quite a drive to gatwick from us (in Lowestoft) so will be staying overnight at the airport, would this increase our chances?
Really prefer the upper deck (as do most people), but left it late in booking this holiday
Any help greatly appreciated.
I presume, being an exit row that row 75 on the Upper Deck cannot be pre-booked, and was wondering what people think are the chances of getting this row at check in?
Would I need to unbook my seats on Row 82 (I would like two seats together so have pre-booked these for the time being), we are going to use the twilight check-in as it is quite a drive to gatwick from us (in Lowestoft) so will be staying overnight at the airport, would this increase our chances?
Really prefer the upper deck (as do most people), but left it late in booking this holiday
