Writing in English, as my svenska has been a somewhat less used, and Thermias are sold outside Sweden too.
Another success story, with a 2006 Thermia Duo 10. As a PoC used two 470 uF 50 V through-hole caps, when it worked fine measured voltages and accordingly replaced by smaller 220 uF 25 V (positive, near down button) and 16 V (negative, near right button) through-hole caps suitably positioned on their sides. Plenty of room for fitting those bigger through-hole elcaps that way, stable enough setup to not need even hot glue, and doesn't need to be pretty inside. Guess those 470 u caps would have fit there as well, but would have needed to be re-installed properly anyway. Pretty much any good condition elcaps with at least 220 uF and 25 Volts (negative side can do with a 16 V one) should be OK.
Detached one pad of the SMD elcaps while desoldering, luckily the ground side for which I found a better place at the down button's feet. If done again, I'd add some solder to the SMD pads, heat them with two soldering irons (or tweezers, if powerful enough) at once and avoid bending.
Thermia really should repair these for free, I have had Canon replace camera image sensors and Onkyo replace an amplifier digital board years after warranty expired as they had too quickly aging components, even if those products have much shorter expected life spans than a ground heat pump. Personally I don't care as it was much less hassle to change them myself, but not everybody are electrical engineers having bagfuls of components like capacitors lying around.
BTW, I'm pretty sure the display uses I2C like the ThermIQ ext connector, as there are two wires connected to the PIC's I2C pins, and why would they choose different protocols for two adjacent similar connectors handling similar data traffic? Dunno why those data/clock wires are also connected to the next GPIO pins in the PIC, maybe to keep them from floating. I'll attach the logic analyzer to the display cable next time when I open the case.