I'm assuming this is a family sized house (rather than a 1-bed place for a couple). In which case:
Washing machine
Decent clothes airer - you can't always dry outside, and not everything can be tumble dried (though a drier would be nice)
Enough heat proof mats for taking things out of the oven - I might have two dishes in the oven, and be using the hob (so can't put additional hot things on there).
Bed linen - towels I don't mind, but we probably don't have the same size beds at home (as we don't have a standard double anywhere in our house, we don't have linen for one).
A super-king bed would really sell it for me - we have one at home, and struggle to fit in a smaller bed.
Downstairs loo - nice, but not essential.
Decent sized TV; we've stayed in places where the TV was smaller than my laptop screen!
Whatever you choose, please please stay in the house for a weekend at least once it's been kitted out for guests - then you'll discover if there's enough light to read in the living room, whether you have enough pots and pans etc. We've stayed in some lovely properties on paper, but where there have been some glaring oversights in the detail. And in others which aren't so posh in the advert, but where the owner clearly stays regularly - e.g. there's a hook for the window that would blow in the wind when open.