ESA Backpay

I have now received all backpay from migrating from Incapacity Benefit Contribution based to ESA Income Related. I was informed on the telephone that I would also receive backpay for my deceased husband who passed away in February 2015. We were both receiving our benefit separately not as a couple and his backpay would be separate to mine. I now found they have paid me as a couple, I wondered if anybody knew if this was right? Surely if we were claiming benefit as 2 separate people we would be paid backpay as separate people, they did admit they made a mistake not paying us way back when, as a couple but I feel they are just trying to save money that was originally owed to us. Your thoughts would be appreciated.