Hadn't thought of this - you might be right, but they still couldn't deny it was a valid route.Or they may not pay you on the basis that you deliberately chose a slower route and therefore effectively delayed yourself?
I decided it wasn't worth claiming anyway - the compensation would be less than £3 as the ticket was cheap anyway! But thanks for the advice!So the lesson there is always arm yourself with the relevant pages, don't pay any extra fares, and don't make any compensation claims!