I agree after reading through this. I think that if you can see the photographer's feet in a photo, that fails the satisfactory check of 3c, because a photo of members at a wedding should never have the feet of the photographer in them.
(3) The quality of goods includes their state and condition; and the following aspects(among others) are in appropriate cases aspects of the quality of goods—
(a) fitness for all the purposes for which goods of that kind are usually supplied;
(b) appearance and finish;
(c) freedom from minor defects;
(d) safety;
(e) durability.
(4) The term mentioned in subsection (1) does not cover anything which makes the quality of the goods unsatisfactory—
(a) which is specifically drawn to the consumer's attention before the contract is made,
(b) where the consumer examines the goods before the contract is made, which that examination ought to reveal, or
(c) in the case of a contract to supply goods by sample, which would have been apparent on a reasonable examination of the sample.
And then you have section 13, that if you can prove your delivered photos don't match the quality of the online or printed portfolio they presented to you. Besides the quality not being the best, I doubt you can see the photographer's feet in any of their portfolio samples, correct?
13) Goods to match a sample
(1) This section applies to a contract to supply goods by reference to a sample of the goods that is seen or examined by the consumer before the contract is made.
(2) Every contract to which this section applies is to be treated as including a term that—
(a) the goods will match the sample except to the extent that any differences between the sample and the goods are brought to the consumer's attention before the contract is made, and
(b) the goods will be free from any defect that makes their quality unsatisfactory
I think the proper solution by the photographer is to reprocess the photos properly this time, and redeliver them, and then issue a partial refund.