ah, so much sweet never-left-London stuff on here...
oil central heating same as gas central heating except you have some control over what you pay; super cheap at the moment so everyone is tanking up whenever they can. You just keep an eye on what's in the tank using a simple gauge. Never let it run out and always get it serviced annually, I pay around £120 for that. Strikes? Maybe in 2000. lack of delivery due to bad weather? Just think ahead for winter and monitor prices. Theft does happen but won't be at the moment. Never lock the tank, just add the oil to the insurance.
ask about age of boiler; if it is over 10 years old it will guzzle fuel. You replace not for financial reasons but to be a bit greener.
those open fireplaces: chimneys lined? Swept? Shouldn't be used as open fires as grossly inefficient, budget for logburners.
if it has a septic tank system, same use as mains sewage (nothing down the toilet except body waste and bog roll). you can't have a waste disposal in the sink (eco nightmare and with a garden that big you have a compost heap) and you need to use washing liquid not washing powder, so buy v. cheap washing machines as they won't last as long.
inside is a bit dated but minus all the old fashioned ornaments and frills will be fine. The important bit is that they look to have redone the bathroom.
I don't know the area but is Alton Towers close enough to be a nuisance? And do you know how to use a lawn tractor?