Commercially option 2 (settlement) is best for them, get money in bank, no further admin time, move staff onto next culprit.
Option 3 (court) takes longer, requires lot more effort, and risk of court agreeing a payment plan so getting funds takes longer and amount not guaranteed.
What no one know is which option they choose, if you skipped paying for full journey from Brighton area to London for months, could easily be £1000+ in avoided fares. When get to that sort of amount they might (not will) take a commercial decision and accept big settlement quickly.