Hi Cheshire and welcome to CAG
As the work was completed and paid for, it's down to the customer to take action against you if they remain unhappy and that could include court action.
Your only problem sounds like the failure to say in writing in your Estimate that "the colour match and finish would match as close as poss but you were working from photos so you cannot guarantee this aspect".
Learn from this and include any agreements, terms, disclaimer, etc in your written Estimate.
1. What was the approx value of the work done ?
2. What would the remedial work cost you including travel, material and labour ?
Even if you visited and redid work, who's to say the customer would then be happy after the friend got involved.
Right, but delaying payment could impact your credit rating and if you default then that won't be remedied until you start paying it and even then it could take several years to wipe.
If the debt isn't in OPs name then no probs but I would rather start paying to hold the collections process until he gets all the info.
This is just like vouchers and gift tokens.
If you tried to return it because you simply have changed your mind then I would say you would have to accept the credit back onto the card if that's what they insisted on. However, because the item is faulty and they are in breach of contract then I think you are entitled to the cash.
Did you complain to the dealership about only having one key back in 2017 when you collected it? If not and this is the first time you've said anything about it to the dealer I can't think how you could ever prove your argument. So yes you probably will have to suck it up and buy a new key. The moral of the story is to complain at the time.
Maybe they can't prove they gave you two keys, but on the other hand you can't prove they didn't and two keys is what's the standard provision by the manufacturer. Go through all the documentation you got when you collected it. Does it mention keys anywhere?