No real help and quite a lot of rude and unhelpful comments.
You did get some useful information.
You didn't initially mention that it wasn't in the UK. I assumed it was in Berks.
Have a look at the Dunsley Neutraliser site, which shows the recommended pipework arrangements for linking solid fuel to gas/oil appliances.
http://www.dunsleyheat.co.uk/neutralizer layouts.html
The neutraliser provides hydraulic separation, i.e., the flow and return pipes of the heat producing devices and heat emitters are connected to it and this avoids nuisance circulation where you don't want it. You could use a heat store or a low loss header for this, but the Dunsley site has useful diagrams.
I'd be very cautious of getting someone to diagnose the problems from the UK; they'd be reliant on your survey, you would quite likely overlook details that are relevant and there will be a language hurdle in getting a local to rectify it.
In the UK, the solid fuel burner should operate by gravity circulation (no pump needed; still works if the power fails) so it would usually be on the ground floor, with a metal feed & expansion cistern in the loft. There are very few solid fuel appliances that can be pressurized and they have elaborate safety devices to dissipate excess heat. The few on the market that are mostly recent EU imports; I'd check the specification of your stove carefully.