Ha - things turned out well on my return journey from France:
Eurostar cancelled my Saturday night train, so I had to stay in a nice Ibis Styles hotel in Lille rather than a crappy hostel in London (it was a stupidly expensive night to stay anywhere in London), so I'll claim for the Ibis Hotel (I couldn't cancel the hostel, so I'm not being dishonest)
I absent-mindedly did my tap in & out on the Underground on my Caisse d'Epargne card on Google Wallet, and the next day I got a notification that the £3 cost had been refused by CdE.
The train from Paddington was delayed by 15 minutes, which meant I missed the connection to Topsham, and that being more than 30 minutes after the scheduled service, I've claimed 50% back from GWR (as it was sold as a connecting train).