I don't know what changed - what made her click.. but Hammy has started whining when she needs to go out to the toilet. We kept her in a large caged area, not a crate and if we are near and she needs to go, she makes a quiet noise and we bring her out and praise her greatly. There have been a couple of accidents (she complains very quietly), but for the most part, its working. Thanks again to all on the post who have given advice.