Part-time nanny for twin girls

We are currently looking for a nanny to look after our twin girls once a week, ideally on a Monday (but we could make another day work if we needed to accommodate someone we really liked). We would need a minimum of 8 hours, ideally 10. We have a full-time nanny who has been with us for 18 months and is trying to reduce her hours to four days a week, potentially even further. So we need someone for one day a week for now but this could lead to more hours, should the candidate be interested.