URGENT - today. Heating engineering brief

We have a wood fired oven which does central heating as well as being an oven. The oven is shown in the following link, using google chrome you can get an automatic translation:

http://metlor.com/produtos/me20/

It has been fitted with a sensor panel of course and a hot water tank, say 200ltr, a little bigger than a standard UK house tank anyway, it was also supposed to have solar thermal but we were running out of money and skipped that to install later, but that aspect should have no bearing on the functionality of the cooker and hot water system. At the time we discussed with the engineer that instead of a radiator could we have some external copper pipe in a coil / zigzag arrangement to use to heat a outside hot water tub of a size of maybe 1.5m cubed. He said yes that that the system would work.

Anyway the hot water tub wasn't fitted as we were still working on the house. The coil was made and then laid outside in the cold air, linked up to the system. The system never worked, as soon as the oven reached about 100oC at best, the water would get too hot and the emergency dump valve would dump all the hot water from the tank. We have been trying everything to get him to fix the system. Eventually we find out that this type of oven actually had to have approx. 60 radiator elements to work, my house is 4m x 4m with 2 floors.

So what I need is someone qualified to make the calculation of exactly how many radiator elements the system needs and then if it didn't have the radiators but had the hot tub, would a hot tub, usual size maybe the measurements I have guessed at above, displace more heat for the system to work.

Also would the water displace the heat better for the system to work than the coil laying on the ground open to the air. The coil he made consists of maybe 4m of regular plumbing copper pipe, un-insulated.

I have to have this work done today by 3pm UK time and would need a copy of your engineering qualifications