Help with Stove central heating

christramp

I have a Stanley Fionn boiler stove, has 28mm pipes into and out of it, hot pipe goes directly up to the loft and feeds down into the tank in the hot press, thermostat attached. 28mm pipe comes out down to a circulation pump that is fitted at ground level and feeds out into another 28mm pipe. It is fantastic at heating water but there is no effect on radiators. I have a decent size radiator system - 15 rads and I know the Fionn is a small output stove but I was thinking of shutting off all rads except for the heat sink in the bathroom - would this work?
If I switch off the thermostat to stop the pump you can really feel the heat on the pipes feeding in, when the pump is on it has a nice steady flow running through the pipes but the temperature on the pipes drop considerably, if this was a closed loop then surely the pipes would remain hot as it would be reheating hot water - I presume this may mean that it is indeed linked to radiators and the small stove output is not enough to heat the rads. Its a bungalow - so no upstairs rads.
My question is how do I tell if it is linked to the radiator system - is the pump simply feeding the return water back ?
Secondly I want to install a larger boiler stove into my front room - it will be directly back to back with the Fionn and if the current back boiler does feed into the radiators I was wanting to know can both be linked into the system.
I hope this makes some sort of sense and somebody can help, I will have the stove installed and a plumber connect it but I need to know how the system works before committing to buy a stove.
Many thanks in advance
Chris