Maternity leave in the UK works for 3 periods of time.
- 6 weeks on 90% of your salary
- 20 weeks on £100 / week (net)
- 26 weeks on nothing
Some companies offer more than this (eg 90% for extra weeks), but if they do so, they often require the person to come back to work for a significant amount of time afterwards, or to repay the money.
For the first 6 months, your employer must keep your job for you. For the second 6 months, they must guarantee you an equivalent job of an equivalent level with the same pay, but it doesn't have to be the same job.