Reg and Pat
Even in our latest caravan we removed the OME carpets and using them as a template cut out fresh ones from an offcut we bought quite cheaply.When we come to sell in go the originals, like new.
Even if you haven't got removable carpets I assume you will carefully cut around all edges thus giving yourself a template.
Tiles shouldn't be any more difficult if you lay them out first and again use the old carpet as a template. Number the reverse of each tile and use a "map" so you know where to put them. Some tiles have to be orientated east west etc every tile to avoid rucking up. Check that.
Cheers
Dustydog