There is a body of evidence which shows that employers who offer specific leave options, combined with financial support for those with caring responsibilities, experience lower staff turnover and better rates of recruitment. Employers are always looking for ways to ensure that key staff are recruited and retained. You can find useful information online on the business case for family-friendly policies. The TUC is constantly updating its information and case studies to support trade unions and employers developing policies to support a better work-life balance.
The TUC and most trade unions can supply you with leaflets and booklets which describe the law covering paid and unpaid family leave including parental leave, flexible working, paternity/maternity support leave, maternity and adoption leave and rights for carers. However, your union may well already have negotiated better family-friendly policies in other workplaces, so it would be worth investigating if this is the case to help you to develop the particular package that you want your employer to agree to.
The TUC's Who's looking after the children: a trade union guide to negotiating childcare (PDF, 1.83MB) can take you through the steps involved in negotiating childcare with your employer.