Bad traders

I'm sad to have to be posting in here.

I recently bought a set of Corima wheels from @Stevethecoffee sold as in near new condition with not much use. They arrived and they are indeed in good condition but I found that the front wheel has some side to side play that seems to stem from a design flaw in the hub or a manufacturing tolerance.
A bit of googling shows someone on weight weenies had a similar problem on a brand new set of wheels, Corima apparently sent them a longer axle which apparently fixed the issue.

The wheels are now out of warranty and I don't have the receipt for them. It seems like the issue could be fixed but I when I bought the wheels I wasn't expecting any issues like this and really don't see why it should be me who now has to deal with it.
I contacted the seller saying I'd like to return the wheels since I'm not happy with them, I expected wheels with no issues.

This is the response I've been given:

I’m going to have to say no I’m afraid based on the fact that when I used the wheels I didn’t notice any issue with their performance which would lead me to investigate any mechanical problem, I’m sorry.
That and the carriage cost me £40 insured which I would likely have to swallow again if I resold them. It’s one of those things with buying sight unseen, you’ve discovered an issue that I didn’t know existed but you’ve got a top tier set of wheels for really cheap which can be sorted out, even if it’s a bit inconvenient.

I offered to pay the return cost and as a gesture half of the £40 paid for postage.

This is the response

Yeah but what you’re calling an issue never was an issue when they were in my possession. I had them, I used them, they worked spot on, there was no issue. You’ve checked them more thoroughly than I ever did and in your opinion there’s something wrong. I would take them for a ride and see if there is an issue then. They’re out of my hands now, I’m not going to get into the admin of chasing something which wasn’t a problem when I was riding them.
I’m not going to take them back, I’m sorry.

I suggested that with that logic then anyone can sell something on the forum and then wash their hands of the sale when there is an issue just by saying "well they were fine when I had them"

the response is:

I sold the frame which had some damage, I highlighted that. I sold the finishing kit but gave the bars away free because they had a score I didn’t like the look of and made sure the buyer was aware of that. If there’s issues with stuff I make sure people know and it gets reflected in the price. I haven’t tried to pull the wool over your eyes. In my experience there was no issue with the wheels, I sold them in good faith. I still believe that if you fit them to your bike you will have a great time on them without any remedial action being necessary.

It suggests that theres actually nothing wrong and I should just ride them!?

I'd dealt with Steve before, I bought an axs groupset from him with no issues, when I bought the wheels I sent the money via friends and family since I had no reason to believe that there would ever be any issue like this.
Of course if I'd used goods and services then an item not as described claim would have quickly settled this.

I'm just really disappointed that Steve has taken the line that he'd never noticed any issue before and so doesn't feel like it has anything to do with him now.
When the parcel arrived he messaged me checking that they hadn't been damaged and that I was happy with them. It surprising that a return is being point blank refused now that I've said I'm not actually happy with them.

I really don't think I'm being unreasonable in asking for a return? Even if it could be relatively easy fix, I shouldn't be stuck with wheels that have a problem just because the seller hadn't noticed it before?

A real shame that this is the stance thats been taken.