Hi all, new to this and need some help and advice, im planning the following trip and having issues with trains/buses as cant seem to find a valid/convenient route. I appreciate the rail pass may not be valid with these countries, in which case alternative transport and/or different routes would be welcomed.

Help with:

1. all the legs marked red I am struggling to find the bus or if there is a train?
2. Also I want to get from Kotor to Lake Ohrid what is the best route? (i have already seen Serbia so ideally can avoid if easier)?
3. The best/cheapest nearest airport to fly back from Lake Ohrid to London

Plan:

Day 5: Zagreb to Hrvatska Kostajnica ,and then walk/taxi, Banja Luka to Sarajevo - is this train running? can I book?

Day 8: I dont think there is a train and this route is by bus? is it better to break this journey up so Kotor - Dubrovnik and then Dubrovnik to Kotor or do it on one bus?

Day 11: what is the best option to get from Kotor to Lake ohrid

Day 14: what is the best/nearest busiest airport to get from Lake ohrid back to london?

Thanks in advance