The British Automatic Sprinkler Associate will provide you with the best resources. See
www.basa.org.ukAlthough I am not familiar with hospitals generally there will be various fire engineering advantages in installing a sprinkler system - things like bigger allowable areas for example might be allowed.
From a cost perspective, in addition to the above, ask your insurer how much the fire premium will be reduced in the building - it could be a very significant discount.
From a practical point of view, the obvious benefit is that they will control with no help needed 99% of fires. Obviously in a building full of people and expensive equipment, this is a pretty significant advantage compared with waiting for the fire brigade to arrive, property damage, exacuation, injury etc.
Going on from this, all the associated costs of a major fire need to be considered, finding suitable alternative accomodation while you rebuild the property, transportation costs, the actual cost of the damaged equipment and building (although most of these costs might be met by the insurer), loss of staff moral, etc should all be considered.
If you incorporate most of these factors, you can make a pretty strong argument for spinklers in most situations.
I am sure that BASA will provide you with amore comprehenisve argument, and that the fire engineers here can explain more on the trade offs in building design that you might be able to do as a result of a sprinkler system. And like I say, run it by your insurers, you might be surprised about how much discount they can offer you with a sprinkler system.