My natural reaction would be to say you should take up the old laminate floor first. Otherwise how will it fit under cupboards, skirting boards etc? Also if for any reason you ever need to get under it, it will be much harder with 2 overlapping layers.
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I don't think wood blinds are that expensive. I was looking at getting 2 105x145cm drop blinds and was getting prices around £60 each when I looked online for custom ones. The drop was not to the floor but just inside the window recess.
I guess it depends on your opinions about quality, time...
This is good advice, it is important to remember that most people expect somewhat of a random appearance as to where planks start and finish rather than the "ladder effect".
I agree you get what you pay for. Laminate flooring is a fraction of the cost of hardwood flooring so I don't think people are expecting the same quality.