I recently moved into my newly built gaff, where I have a wood pellet boiler and UFH (Roth piping etc.). Researched the options quite extensively, and find that this set up is working just fine. Also installed a dual coil hot tank, as I was considering solar panels for DHW, but am thinking again about this, as the WPB is supplying plenty of hot water, and is quite efficient in that respect.
Also considered having a buffer tank, but didn't go with it in the end, but the UFH seems to be working out just fine without it.
Can't remember off the top of my head what the boilers output was, but it was too high for my requirements, and so had it turned down by the installer after a couple of weeks, pretty easy as it is just a function of how quickly the delivery system sends pellets to the boiler.
One thing about the WPB is that it does require a bit of maintenance, which I am more than happy to do, though those who are less hands on may not appreciate this aspect of the system. I need to fill the hopper about once a week, as I didn't go for the direct feed from my storage silo, and the combustion chamber needs to be cleaned and ash removed every so often, about every couple of weeks (could probably do it a lot less), takes ten minutes, tops, and is really simple.
The pellets for the system are stored in a self built silo in my garage, beside the boiler, fireproofed on the side facing the boiler (tis built from ply), and the pellets seem to be burning just fine, no problems with quality whatsoever. Very little ash, remove dust from pellets while filling by using a wire guaze bucket, couldn't be happier really.
Got the pellets within two weeks from Balcas, and I know there are others suppliers of pellets now available, though I'll probably stick with them as they're quite close to me (am in north west).
Net cost of installation was around 2K, got the grant of €4200 after installation, thoughy I know theres a second phase of grants which may be a little lower, though not as reduced as the grant for the heat pump systems.
All in all, I am happy with the choice of system, its working just fine, and I would recommend it to those who like to be hands on.