In terms of the ewes, there is likely to be some immunity gained from natural infection, so should have no problems next year, as far as the experts are saying.
The problem is when the ewe is infected at a certain point in early pregnancy, the virus then goes into the nervous system of the lamb, causing it to not move around as normal in the womb, and stiffen up and get these funny joints.
I would be tempted not to keep any of the affected lambs (send away fat/store instead, as they should be OK as long as not lame), mainly because odd joints are more likely to be under strain later on in life, and cause earlier arthritis/lameness issues, particularly if put in lamb and bearing extra weight and metabolic stresses.
If you have problems in your homebred ewes, then I would vaccinate next year, if not, it would suggest you don't have schmallenberg in your area, and so it's less likely the ewes will get affected at the wrong time of pregnancy next year. The virus only lives a very short time in the blood, so the in lamb ewes likely got infected before they came to you, and likely didn't have any virus in the blood to be picked up by your local midges to spread onwards.
Fingers crossed for your homebred ewes and hopefully that will be an end of the problems for you.
Hope that helps
Suzanne