Elizabeth shouldn't worry. If you're taking ordinary maternity leave (the paid period of 26 weeks), rest assured that you have the right to go back to exactly the same job. If you take 26 weeks' additional maternity leave, things are slightly different. In most companies, you're still entitled to return to your old job unless your employer can demonstrate it's not reasonably practical to have kept it open for you. But this doesn't include simply liking your replacement more.
Lots of women worry about their replacement outshining them, but it rarely happens. Mostly, the boss is overjoyed to have the new mum back, so just relax and enjoy your leave!
Once you're on your maternity break, you need to think about childcare for when you return to work. To find out what's available locally go to www.childcarelink.gov.uk or phone 0800 2346346. For more local info on childminders, nanny share schemes, nurseries and playgroups, contact the Children's Information Service (ask at your local library, or call the council). Or log on to the website of the National Association of Children's Information Services at www.nacis.org.uk. Also ask around - the best info tends to come from other mums.