Thanks for the input and info on Rayburns everyone, most helpful!
You can run a rayburn with the water tank in but disconnected - but I wouldn't recommend using the tank thereafter.
I've got a mind to remove it if I do go ahead and get the one offered as I can see how I would use it to deliver underfloor heating using a proportional control valve to split between the floor loops and a heat dump radiator, but would need to work through in some detail to justify the setup to Building Control, so better as an add-on project.
But if I can't (or don't want to) persue that, if the boiler has been preserved I can always sell it on to recoup some of my costs.
It has a huge thermal inertia so you need to plan ahead. It wouldn't really suit people who were out all day every day. It would use about two wheelbarrowfuls of wood per day - fed at regular intervals - or one hod of coal fed twice. It gives a nice dry warmth and we like it but wouldn't want to rely on it as our primary stove/heating!
That sounds like it's actually a good fit, the house itself is stone with substantial thermal inertia of it's own which generally drags things in the opposite direction to the one I would want during winter and the central heating is completely unable to heat the kitchen (mainly down to poor system design) and my office which sits above it.
I work from home, so being in isn't an issue either, although based on the fuel consumption I guess I would need to go down the solid fuel route.
I definitely wouldn't be switching to only a Rayburn for cooking, after growing up in a house where the DHW was from a back boiler I know how grim being forced to burn a fire when it's warm is.
it had the back boiler and was hooked up to an underfloor heating system.
I don't suppose you know any more about how that was set up do you?
It seems like it's a bit awkward to run underfloor heating on solid fuel (at least under the current building regs) and there's no obvious commercial solutions out there.
They were a great improvement on the open fire range but superseded by gas or electric appliances about 100 years ago
This gave me a good giggle, you're not wrong mind.
I've had two. They are a disaster in terms of cooking unless you keep them lit permanently and spend a fortune on fuel.
...
They keep the kitchen nice and warm, whether or not you want it too.
I can see the fuel efficiency/cost issue clear as day... But given I currently spend quite a lot on electricity trying to keep my office above the kitchen even vaugely habitable from November to April, and it's effectively wasted money if I even try to heat the kitchen with the central heating at all, I'm not so terribly concerned as I otherwise might be.
There's a reasonable argument that I'd be better replacing the boiler with a bigger one, and installing additional radiators... But it's only a 3 year old system, and it's a choice between Free (ish) and spending a whole lot of cash, so the numbers stack up in favour of the Rayburn short term.