Any probs with spilt coolant inside the engine bay?
None. as for washing the engine bay, I've done many & never had any issues, just resist the temptation of washing the engine cover otherwise wash away. fast swift movements, wash each area 2 or 3 times rather than one long soak. remove the engine cover to wash it.
I've cleaned the engine bay of my 147 a few times. Just use a cloth and wring it out as much as you can so that you are left with a damp cloth and use some elbow grease. It takes patience and effort but it's a lot safer than splashing water around the engine bay.
As others have said, leave well alone unless you want to get in there with some degreaser, a tooth brush and one of those garden water spray things that you pump up. I'd never risk a steam clean or a hose pipe and certainly not a jet wash.
I love to see a clean engine bay and in the past I have spent hours with pressure and steam cleaners, polish and other potions, however, I would not put anything that has water in it anywere near my 156. As has been said water and electricity do not mix and I would not risk the fragile Alfa connections.