And re IHT, just to be clear, even if the spouse died many years before, it still gets added to the recently deceased person's estate.
My mum died in 2012 and my dad last year
; the house was valued at £450k and the rest of the estate is worth nowhere near £550k so there will be no IHT payable.
Barring a few small bequests, it's been left to db and me, with a small proportion to the grandchildren. I'd still rather have my dad around 