Mate is was not expensive, my workmates are qualified builder and stone masons so they rebuilt the chimney back that was under the roof tiles took them a day and a half, cost me €390 plus a few bricks and the mortar, oven is second hand as it is hard to find one in Germany at the moment. Just got to do the shop downstairs now for my wife as it can get nippy and I don't want the gas on if I can help it. Yours looks like it does the job? Perhaps you could get one of those stainless steel chimney's that go on the side of the house, they are not too expensive and a cheep oven?