20 year old house could be a lot wrong or nothing, masses of new builds have issues....many of them never get their snagging lists dealt with - you only have to look at this forum to see this
If the bedrooms all have laminate it could just be the sub floor was poor or non existent ie they put the laminate directly on the joists. Or it could be more serious and the tie ins for the joists are gone/broken/missing
Was the ceiling below the affected bedroom ok?
At the end of the day a surveyor May point you off in the direction of a specialist, however you’ll get pointed in the right direction in the first place. I disagree that surveyors don’t tell you what’s wrong, they do if they can see the issue without having to disturb the fabric of the building, that is not always possible but they will give you reasoning for their findings.
The surveyor will also look at the rest of the house without rose tinted glasses and make sure you are not paying for a lemon
A builder is also a good starting point imo if there is only one or two direct issues you need an opinion on, however they will also not be able to disturb the fabric of the building until you own it, so much of a muchness. The difference is a surveyor is trained in housing defects specifically.
Oh, and a valuation survey is not a building survey, it is a valuation only. You need to go to the more expensive surveys for what you are looking for.
I hope that helps