In my experience of installing and running 4 stoves in 2 houses I would tend to go for higher output stoves than the conventional stove sizing calcs would suggest but not too large. The logic being that running smaller stoves hot will reduce the life of the stove and require more frequent filling with smaller sized logs. Also, we now seem to live in slightly more troubled times and the log burner gets you to be independent of gas/electricity in the event of power cuts/storms etc. A flat top could also give the option of slow cooked casseroles etc. Consider also what type of stove - woodburner, multifuel, radiant or convector.
You may get 'freeish' logs from a mate but these tend to be more more gnarly difficult to split stuff that the firewood guys cant be bothered to convert. It takes a lot of work and you should start now if you are thinking of a stove in 12 -18 months time - get a chainsaw now and start stacking, get PPE, a bit of training, a couple of mauls, splitting wedges, build a log store, hope your dear wife doesn't mind the garden being given over to log processing and storage and that your neighbours don't mind you using the chainsaw at weekends. Finally, don't expect the kids to help out -they probably won't :roll:
This question has been asked before on this forum - might be some useful info there. Above all speak with the stove installers but like any trades there will be gooduns and not so. I think a couple of vendors lurk on Green Living and they seem to give straight advice.
Sorry for the verbage but as you appreciate there is a lot for you to think about.
A pile I did earlier this year