Help!!

[starcruiser]

Manged to spill acetone - nail polish remover onto a large wooden window sill.
Have sanded it and thought I could just stain the whole thing but it won't take the colour.
Any advice gratefully received.

I would try something like this:
www.amazon.co.uk/dp/B003F1I2EC/ref=asc_df_B003F1I2EC58473574/?tag=mumsnetforum-21
Google "wood crayons" - there are many types available.

Find the appropriate colour for your wood and colour the bleached spot only. Apply in small amounts and let the colour build up gradually, ie let it dry between coats and then add more if needed.

Was it varnished? Varnish (particularly the old oil based stuff) penetrates the wood so it can take a lot of sanding to remove it. Could you try a coloured varnish instead of whatever it is you've used so far?