Cost of electric

Hi, Yes this is quite excesive. It looks you don't take good profit from the night and day tarifs. First, as for you don't have gas, you will have a boiler for hot water. Put it on a timer, so it heats the water at night. With normal use, and not a very small boiler, you can do with one time at night the whole day. 
Second, for the amount of kWh you have used on daytime, you probably use an aircon. You want to keep control of the bills? Put it off and use a fan instead. Much cheaper. 
And with winter coming now, heat your house up in the morning, and be careful with electric heating on the 'expensive' hours.
Third, Cook in the mornings, and just warm it up at the time you go eating. Of course, when possible. 
And than, last but not least, look at the 'potencia' you have contracted. Calculate your electrics and make sure you're not overdone. Lowering it (if possible due to use) will bring an extra cost, but you might earn it back on your bill.

I spend 1/3 part of my usage on the expensive hours and 2/3 on the cheap hours. Just to show you how you can take profit of separate hours. 
If you're not able to take these measures, change your contract to the normal tariff, because you're using now too much on expensive hours.

Our bills are monthly and over the last five months have averaged €70 for a three bed apartment, two people. They were at their highest in summer when the aircon was in use. 

The water heater is outside and is not separately controlled. Our SCs don’t seem excessive. But we know that electricity in Spain is the highest in Europe and pro rata it costs about twice what we spent each month in the U.K. However, because we don’t have gas bills we are still making savings overall on our UK fuel bills.

Many thanks for your reply. I’m taking it night time is slightly cheaper rate . I know our neighbours who are resident in Spain have a different rate and their electric, I believe is free overnight .

Looking at our bill, it’s not much difference from night / day rate .

Andy 

If the part of the bill you posted in your initial post is a part of your bill, than you have simply a day/night tarif. There are no different day and night tarifs, for everybody that has it: at the 'low' hours, the price for 1 kWh is half the price for 1 kWh in the 'high' hours.