When we realised that there could be a fine, after the phone call from the SS, we contacted the Nottinghamshire County Council, and they advised us in order to abide the law, we had to send the HT a letter that we took our daughter out early for home education. We did that, and there was no drama afterwards.
ReallyTired, we withdrew our daughter from that horrible school shortly afterwards, because they didn't care about our DC's medical needs.