Answers:
In a ideal world , it would be best too lift the laminate up first , in case there is any moisture in the sub floor .
Fitting new underlay and grippers on the foam insulation, could cause condensation and make the carpet bubble , underlay should be fit in one layer ,straight too the sub floor .
Has long as the fitter are careful it is ok to fit with a marble table in the room , although after time you will have dents in the carpet from the weight .
All carpets fit under doorbars , they should of changed bar to suit .
It is always best too decorate first , and leave it a couple of weeks before flooring is fitted .