Hello Matt.
Ok, you purchased it second hand from an indoor market, so I assume you paid cash ?, or was it on a credit or debit card, you see where I am going, you can track the payment, if you paid by card.
Sometimes markets sell equipment that has been repaired or returned to companies with faults, these graded items are still covered by the sale of goods act, unless stated otherwise.
If it was purcahsed second hand, then I assume the buyer may well of filled out the warrenty form.
However sometimes the warrenty is made void by another person not authorised to repair doing a repair.
I don't know how the transfer of goods and their warrenty is affected, but all goods are numbered, so the track back is easy for a large company.
I would go straght to your local council trading standards team and ask advice, or pop into the local citerzens advice centre.
Good luck