Personally no I don't think there is anything wrong with replacing with smaller machine. 8kg washing machine is very big and 6Kg should do most families especially one with two kids. End of day they are getting a new machine. Any point in checking out to see if there is anything like The Good Guys in Scotland where you might be able to get it a bit cheaper because the box was damaged etc?

Only thing i would say is don't go for very cheap brand. Prior to buying our house when we were renting our cooker had to be replaced and owners went for the cheapest of the cheap cookers and it was #rap to cook on and really cheesed us off.