Curiously, we've gone through the same process at our house, so I can advise from experience. First, give them a good hoovering, especially into the gaps, to remove all dust (and have a look at the dust bag in case you've collected early coins or nails). Then, if there are still remains of paint or varnish, try really vigorous sweeping, tackling greasy bits with a detergent based industrial floor cleaner. When they're as clean as you want remember, they're supposed to look old, so don't tidy them too much polish them with a good clear wax.
We recommend Classic Wax from Flat
Paints, Burnham-on-Crouch, Essex (01621 785173;
www.flagfinishes.co.uk). This gives a quick action shine and is just
as good on walls and furniture (it's used by antique dealers who want a
quick effect). To fill the gaps, look for old planks of oak in
reclamation yards, which will be tough as iron. If you have to use new
oak, stain it first before cutting. Watered down black ink is good for
this, rather than official stains, which tend to accentuate the grain.
If you want to be really clever, add 'accidental' stains across your old
and new sections to give the impression that the new fillets were put in
during the 18th, not 21st, century. Our wax hasn't been renewed for more
than 12 years, and is still smooth and sheeny. 'Red Wine on the Carpet'
by Mrs Danvers (published by Susan Hill Press, £12.99) has now been
reprinted, and can be obtained by calling the publishers on 01939 261616