Prity Woodburning Boiler

In an attempt to make living more affordable we are installing a woodburning boiler at Krys' house. Having looked around for a while at specs & prices we settled on an Eastern European, Bulgarian, I think, made one. It's made of welded steel rather than cast iron which may account for the lower cost? However, how complicated does it need to be, it's a metal tank with a fire under it!
As this is going to be located in the cellar we're damp-proofing the wall first, or trying to...