It's worth pointing out that Section 75 of the Consumer credit act does not, in itself, provide grounds for a claim against a supplier. You must also have a valid claim of breach of contract or misrepresentation under other law, such as the Sale of Goods Act or the Misrepresentation Act. If you do, then you have a like claim against the card provider for the full amount of the purchase.
In your case it's straightforward - Jessops charged your card account, but have failed to supply the goods, that makes your claim against them one of breach of contract, so you have a like claim against your card provider.
Your claim will therefore succeed.