hi andy,
there is no reason for the wood to turn black, if you sand it to bear wood, then fill the gaps if any, you will not get that "butamen through"

, please please please do not use bourne seal, quick drying or not, the fumes will go through the house and it will be there for weeks,
i have done over a hundred parquets, had no trouble, sand the floor with the grain cornere to corner then back again, gradualy go through the grains, 36, 40, 60, 80,120. then scotch mesh with 60 grit disc using a rotary machine, hoover everywhere, then aply the varnish or oil, the best on the market with low odour is bona, you can apply three coats of varnish in a day, oil you can do with a rotary machine in 2 - 3 hours,
hope this helps

tahnx jonny