retailer has given me £16
You might find it difficult to obtain more than that if you accept that 'good will gesture'. It complicates the situation. I'd refuse it and hold out for more.
Small claims process is very straightforward.
You can create a claim, save it and use that reference to give the people the claim is against a deadline for settling.
Your claim should also include a rate of interest if they don't respond by your deadline, which will incentivise them to settle.
It will cost any large organisation so much more to fight such a claim, they many will just have a limit up to which they can settle regardless of the strength of the claim
There are limited methods to force them to actually pay up either in advance settlement or if ordered to pay. Most reputable organisations do not want to be public ally Shane's on twitter or social media / their web site.
If you win your claim, they won't want to have that known publicly, so you are likely to get more than £16 if you keep at it.
https://www.gov.uk/make-court-claim-for-moneyy*
The £16 means they have accepted there is a case to answer. I agree about the principle of making them make a decent, proportionate compensation. Send it back and ask for a decent offer to avoid a claim against them. Good luck.
Good luck.