Can't give you an idea of costs but do suggest you think very carefully about how to use the storage heaters in the most effective and economical way as I imagine you are probably on some kind of Economy 7 tarriff which gives you cheap overnight heating. If this is the case, get yourself a timer for your washing machine and programme it so that it switches on and operates during the cheap tariff hours (normally from midnight to about 7.30 am during winter)
Also, check the weather forecast every night and adjust your heaters accordingly, i.e. if a mild winter day is forecast, you won't need to have your heaters taking input at the full rate and you can turn them down to a lower setting for 24 hours. If you can get into the habit of doing this on a daily basis, you could keep your electricity bills to a minimum. Also, try to boil your breakfast kettles, use your toaster, etc. before the cheap rate tariff switches itself off every morning. It normally ends an hour earlier in winter months than it does during the summer, so you might have to get up a bit earlier to take advantage of the cheaper electricity rates!.