Hi Jessica
My advice would be do not drive it until you have sorted the leak as you risk serious damage. The V8 is known to have issues with both its water pump and pipe work. Both are relatively cheap and easy to fix. The plastic fittings (such as elbows) used in the cooling system tend to crack with age so if one has gone you might want to consider replacing all of them at the same time for peace of mind. The S Type is a lovely car but it is 20 years old so if using as a daily driver you need to get ahead of the game and make sure you address issues as soon as they arise or ideally do the preventative maintenance to stop them arising in the first place.
I hope you get it sorted and enjoy driving it as much as I enjoy my 21 yr old X Type.
Regards
John