Try the marriages flubenvet premedicated pellets Chickenfan, they are in stock here which is where I buy mine from.
http://www.farmandpetplace.co.uk/products/poultry/feeders/marriage-layers-pellets-flubenvet-20kg-layers-pellets-with-wormer.html
Mixed results with prolapses, one young bird who really struggled for a couple of months to produce hard shells when first laying, her prolapse eventually righted itself after being shoved back in a few times and one of the ex batts we picked up in March came to us with a prolapse, on and off egg bound every 3 days before plopping out soft shells, nothing to do with her at that stage though it surprised me that she hadn't been weeded out by the farmer as she couldn't have been productive for a long time. Unfortunately she died in her sleep a couple of weeks ago but had generally been quite sprightly and had a nice three months with us. I think you need to balance current quality of life, future quality of life and survival chance when coming to a decision, this bird I may have culled personally on the info given but easy for me to say.