Maybe you could try the ITN website and go thru a booking until you get to the seat selection stage:

-select one way, then
-enter your dates/times/class etc. .
-select your flight from the next page and continue
-select electonic tickets and continue
-enter dummy details and continue
A seat map, if available will appear. It would be on the right of the screen.

At this point you can back out as you have not yet made a booking.

Good Luck...