I can give you an update. It looks like the ewe that stole the lamb has done the right thing. The other ewe has no milk on one side and mastitis on the other and both teats are very sore, sadly I did think this may happen.
these ewes both lambed 24 hrs between them about a week ago, i had to take the one ewe in for 24hours as it got very wet, cold and covered in mud due to her lambing on a mole hill in the rain! so bonding was no issue. These 2 ewes are very bonded as sisters and had been previous hand rears themselves (so pretty tame and halter broken!)
WIll get the sick ewe treated and leave her lamb with her sister hopefully all will be well.
thank you for your kind responses.