Of course gents! Just making sure it all went smoothly so I could write up the full story

So after being rejected initially, I decided to email customer service again (not the particular agent I was dealing with) and ask very politely if I could return the graphics card. Lo and behold, the same guy replies (who I was talking to initially) saying he will recheck my request again on Monday (as it was a Friday). After not being emailed on Tuesday, I emailed again asking what the decision was, and they replied with this:
"It's a change of mind return which has been opened and installed on your
system, if you still wish to return it we will need to charge you a
restocking fee."
I said that under the DSR I don't believe they could charge me a restocking fee. They then replied with:
"DSR states that if a customer returns an item unused and unopened then there
is no restocking fee. However, when the item has been used "more than
examined", then we can charge you the restocking fee based on the condition.
However, if the item's condition is as new then there will be no charge but
you will need to send the item yourself."
And that's pretty much it! They sent me and RMA number and asked me to adjust my feedback on trustpilot (I kept the original review and just made an edit at the bottom), I returned it and got refunded. I actually asked him why they changed their mind and he said it was because my return had to be approved by "the board". So I asked why he couldn't of just said in the first place to avoid confrontation, and it was because "he had no option", he had to decline my return until he chased it up with "the board". Hmmmm.
So after all that, being persistent was worth it! Thanks for all your help guys!