Cows on the Line are outside of railway control & thus don't count for compensation.
(although I have argued unsuccessfully in the past that NR» are responsible for all line-side fencing and thus could be within railway control - their argument is that a farmer could leave a gate open, so is considered outside their control)
So a claim to whoever ran SWT▸ /SWR» at the time of the signalling problems should get your outward claim.
You need to ascertain why you were re-routed in order to provide further info.
Thanks Chris. The rerouting was due to a broken down freight train which we literally went over on the way back from Southampton to Basingstoke. I guess there aren't too many places on that route where there are tracks that pass over each other - but I stand to be corrected!