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Id look into it and try to find a solution before you move in. Often when that stuff is put up in a domestic setting because at the time it was seen as a cheap way of hiding a big mess.
Have you had the surveyors round to the place yet? If not just ask them to assess it when they do go. If they have been ask them if the had a look up there I'd expect any decent surveyor to be curious as to why it's there even if it's not in the report.
Plasterboard will be too heavy for the grid to support without adding more anchor points into the ceiling.
False ceilings are used in offices as its easy to move fixtures as the seating plan changes, hide bare pipework and bad wiring.
Rip it out and ask for money off in the purchase price.
Also the tiles collapse in a soggy mess if you have a water leak from above.