Chris,

Sorry, when I said blowing both hoses off, I meant blowing the top hose off twice. The original firstly, then your replacement.
I agree, I would make sense if all of the hoses were blowing off.
One other way you might check for the head gasket scenario, is by running the car from cold with the pressure cap off.
Often, as the car warms up, the coolant can overflow from the coolant neck. Be careful here - the coolant can spurt out suddenly.
If this is the case it lends weight to the gasket thing.
You can tell I've gone through this a few months ago!

There are several threads that may help you further.
Good luck, hope it's not the gasket.

Barry

E200 Wagon 1994 108k miles.