We took the seat out and have narrowed down the problem, see below for picture with an arrow pointing to the bit that is faulty as i'm not sure what the part is called, basically there are 2 bolts going either side, 1 of them is missing and the other one was loose, the thread is worn though, we've managed to tighten up the remaining bolt which has cured the problem but I have a feeling it will work it's way loose again, do you know if this is a part that can be ordered or would I have to replace the whole mechanism? The one pictured is not my actual one it's just the best pic I could find