help with floating floor pipe access(how to patch floating floor)

Hi all,
Pls excuse me, as I am no builder, but I am looking for advice.
my 1980's house had a floating floor. the subfloor is beam and block, with 18mm of polystrene, DPC sheet, and then 18mm chipboard.
The pipework is somewhat dubious, and "groans" under certain areas of the floor, which worries me that the pipes are rubbing against the block and beam.
I have never had a house with a floating floor before. If I am to cut a section out, how does one replace?
Batten around the edge of the cut out area and screw the 2 parts together? Since there are no beams, I cannot see how else to repair / access without ripping up the whole floor!
Any advice / weblinks would be good, I cannot find much on the groups about this repair, and my collins DIY book does not cover it either ;-)
Many thanks!
Jon
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