Pete, I thought of using a wood stove with backboiler but I was told there is not enough space for it, plus the wood stove is not in the middle of the cabin but in the front, which I know is not ideal for a backboiler. I actually very much like my wood stove, during the weekends I can get a nice fire going on, the problem is during the week, the boat is freezing cold when I'm back from work in the evenings. When I bought the boat the surveyor suggested the diesel heater + timer solution, he estimated the same as the broker, around 3K. I appreciate what NMEA says, perhaps I should take the boat down to the South Dock for a proper quotation, I somehow trust that the broker and the surveyor are not wrong, it's not my plan to stop using the wood stove, I would use the radiators mainly at night and the timer to warm-up the boat before I get back, I'm not expecting to use it non-stop or as the only source of heating, I guess I would make use of them as OldGoat describes. To reply to one of the posts, it's a tug style narrowboat, here are some pictures (interior is not red and green anymore, that was a bit too intense):
I'm reading everyone's posts, it's all very useful and I'm learning a lot, thanks again for sharing.