Agree with most posts.
Although had managed to find DH in my early 20s, didn't remotely want children until my early 30s, as I was too busy enjoying uni, career, going out, trying to be more financially secure, doing up house to make it fit for potential children etc.
We are lucky that we live in an enlightened western society that enables us to make these choices. Most women in the world are not so fortunate.
Obviously it is biologically better to have children at your physical peak in your 20s but our society generally encourages us to leave it later as it wants us to be economically active for as long as possible and taking time out to have children is not an economically attractive prospect (although fair play to Mr Brown with his tax credits and improved maternity allowances).
If the Government is concerned about fertility or reproductive rates, imo, the obvious thing is to make it more economically attractive i.e. improved employment rights (many friends of mine are on short-term contracts in professional jobs and hence do not even qualify for statutory maternity benefits), much more generous maternity allowances (both pay and time allowed off), child benefit and tax credits plus improved support for childcare costs.