In fanfic, putting characters into a romantic relationship, such as writing Ash + Misty from Pokemon as a couple. Often plays on perceived chemistry between characters in the original series. Abbreviated form of the word relationshipping.
These fanfics are just a load of shipping. There's no plot...
Standing or sitting in the sections between carriages on a busy train, 'cos all the seats are taken.
Usually on an unplanned long-distance trip, where the seats are all booked in advance.
About as far from first class as you can get without going outside the train.
After missing the train we'd booked seats on, we had to travel corridor class until we got to Birmingham.
'The Internet', in a stereotypical Northern English accent in which the word 'the' is shortened to 't'. Used normally in a tongue-in-cheek or self-parodying fashion. The word 'tinterweb' also exists, but is rarely used.
Research? Log onto tinternet and let's see what we can find.