My family was in this position just over a year ago when my mother died just 2 months after being diagnosed with cancer. At such a late stage in someones life I think that there is very little you can do to avoid paying the tax, but please note that the 40 per cent only applies to anything OVER the inheritance tax threshold (about �260,000), not on the whole estate. I just looked on it as money owed by my mother, not myself as her house had appreciated in value an awful lot over the past few years and if it wasn't for that we wouldn't have the money we have got now!
I personally think that it's not worth trying to defraud the tax man (they do check these things you know) and just pay the tax and be grateful for what you're left with. It usually serves as a good reminder to other people though, after my mothers death my in-laws have had a good rethink about their finances.