Gtojohn
Solar hot water heating is quite viable however it must be applied properly. The low energy space heating will work but it has to be distributed well or a level of comfort will not be reached. You hadn't mentioned how far your construction has proceeded but the best method to distribute the heat is in-floor heated concrete. This is indeed the holy grail.
If your only thinking hot water for domestic uses you have enough panel but for space heating you will require more panel area. It is recommended 10-30%of floor area but I would strongly suggest the higher end of 30%
I would also suggest for space heating with a concrete floor to install a dedicated in-floor loop which will carry the heated fluid directly from the panels to the floor this way you will have no losses from heat exchangers.
Your thoughts of care free heating of your cottage is a reality. Yes a PV driven pump with solar hot water panels heating your floor and ultimately your space will work and very well but the manner of collection and distribution needs to be done properly.
Randen
