I find for most transactions I can get the same or better deal on TopCashback.co.uk, who seem to track purchases much more reliably and consistently. And has the added bonus of having a choice of redemption options including Avios.

The only exception is John Lewis when intending to make a claim for a Never Knowingly Undersold refund as I know BA Store will generally amend the amount to reflect the part refund rather than entirely decline it.