You could be asked for proof of onward travel. There are no international flights from Newquay
As I quite intensely follow all news/reports etc-also from the ´official' forum they run (as does Rian v.d. Borgt, THE Belgian expert on it and all INTErn. fare-errors), reports on asking for such ´proofs'is only reported from UK. Probably also to do with the intense fear there seems to reign there about fare-evasion and the gross difference (as shown about in 7-d IR vs. 7-d Network GB) in fare levels. So a LOndoner going to Cornwall to ´exit´ UK for the continent does indeed seem a bit odd. But then obviously the most natural way for us on the continent is to simply board a train going over the border-usually plenty to choose from.
About these discounts: as reported most often 2, sometimes 3/yr for 10, not so much anymore 15%, with still full yr to use. OR if higher discount-20%-then only valid in slow season=winter half year. In the distant past they often did larger discounts for winter season only passes.
But the old style young teeners rambling along to see as much as can do countries on the EUR continent also seems to have given way to seniors with too much money and time on hand to do-well,exactly the same!
BTW-the much bigger discount in prices has been offered to NON-EUR people, who had to use EUrail (mistakenly quite a few Brits now seem to think they also belong to that category) which was-after the student yrs had passed was only 1st class and way more expensive as IR. That was when both schemes were merged to what is in fact the very same pricing chart. But with EUrail -most often sold in packages by far away travel -agents then, much more special offers or comboś with other touristic offers was in place. PLUS the chance to make commission-money on selling a few to younger students when in uni in the US after you had done your won stint.