UFH buffer and DHW cylinder configuration

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Liquorice" saying something like:

Ding.

Exactly. Nothing in the gravity lines that might block them.

However... a few years ago I was in a large bungalow where the back boiler fed a hot cylinder on the same floor level. The pipes went up to the attic space, 5 metres along the floor there, down to the hot press and into the hot cylinder. It was horribly inefficient compared to a short run, but it did work, though gawd knows how.