If you are going to live there long term (10 years+), then arrange the house how it suits you.
Who knows what the market will be like when you sell, so you might aswell have the house as you like it whilst you live there.
You can always add a wall back in if when you go to sell you need a third bedroom again.
If you do take out the 3rd bedroom, then you will change your house from a family house on the small side to a house with one nice bedroom and a spare room, to suit either a single child family, one with 2 same sex children (if you can fit 2 in the second room), a single person, or a couple. I would say that that would probalby widen your field, but could not say what price impact not selling to a family would have.
Best to do what you would prefer, and forget about sales prices until you really have to think about it.
Ary.
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