Whatever you do, don't go sleeping on the sofa as suggested. These things are absolutely mental. If you move to the sofa, they will follow you there. The can detect the carbon dioxide from pretty far away. Plus all it takes is one on your shoe, walk it to the living room and then they will all be on their way. You need to try and keep them in a contained area so they don't spread.
As for sleeping in the bed for two weeks, it is the best thing to do. By sleeping in your bed, you're bringing them out into the open, this is when they die. Due to them hiding away, whatever the pest control use doesn't actually kill them instantly. It requires them coming out into the open, and then dying! You'll start to see plenty on the floor in the morning! Hoover them up, then get rid of the bag instantly. You don't want one to still be alive, and them having another infestation popping up somewhere else in the house. The other thing to do. Double sided tape around the feet of your bed. They definitely can't get up past that stuff!
One final thing to keep in mind. These buggers hide EVERYWHERE! Not just in cracks and wooden bed frames. EVERYWHERE. From the picture, I see you have a clock and a lamp on the bedside table. They hide in electronically items and lamps happily. I would suggest everything that you have had in that room, if you can, putting what you can inside a ziplock bag, then inside a black bag, then make it as hot as possible. 40+ is what you're looking for. In a tumble dryer always works too.
All I can say is, you're braver than I. We had a small problem with these a few years ago....I moved out instantly, and I still have some of my stuff in ziplock bags in storage, as these things can take up to a year and a half to die without feeding. So I put a bunch of stuff away in storage to kill any of them. Need to actually pick it up again!
I would definitely get rid of the mattress just for peace of mind!
Hope all goes well! I would;t bother trying to drown them, I'm not sure they drown took easily. the best thing you can do is put them inside a ziplock bag and nuke them in the microwave or dryer. Heat is the quickest and most guaranteed way of killing them for good!