Heater only blowing cold air

[h7fal]

I think from what I'm seeing in other threads the pipes are the wrong way round. Just had an engine out replacement of all perishables so it does seem likely - photo below. My real question is - are these full of coolant that will pish all over the place if I swap them over?

[Cloggy Saint]

The pipe from the thermostat should be on the top stub, so it does look as if yours are the wrong way around. You will lose a certain amount of coolant but if you clamp the hoses before swapping it will be negligable.

[Brianmoooore]

The pipes are just about at the highest point of the system, so the flow from them won't be great when you pull them off. Lift them up to the bonnet line as you pull them off, and the flow will stop.
Fill the coolant bottle to the top before you start, push the hose from the back of the head onto the bottom stub first, then push the top pipe on while coolant is flowing slowly from each side. This avoids getting an air lock in the heater loop.

[h7fal]

Thanks for that - I'll give it a shot during Xmas break.