We run a small business - 3 employees, and have had a couple of maternity leaves in the past 5 years. Finding a replacement isn't normally hard, managing the SMP is fine (as other posters have mnetioned, you just need to claim the rebate). The tricky part is managing the respective rights and expectations of the absent mother adn the present temporary person.
I currentlyhave one person off with her 4 month old. We need to take on - right now- a part timer to expand our capacity in her area of expertise. I can't wait 5 months to do this. So i'll have to create this post, in almost certainty that my mat leave person will want to come back in a couple of months, also part time. At which point i either refuse her on the grounds that. There are now no part time hours available (don't want to do this as we like her, great worker, asset to the business), or get rid of new part- timer to create an opening (write off my rercruitment and training costs), or end the contract for her mat cover person (also a pity, she's v good) and end up with three part timers to achieve the same total hours and coverage. I know this isn't the fault of any of the individuals, or of the female gender as a whole, but it makes lots of tough calls for small businesses. Some of us really are trying our best to do the right thing for everyone in a tough recession!