EDIT: REMOVED COMMENT DUE TO INACCURACY REGARDING RIGHT TO REJECT
I hadn't realised that the right to reject clause is only short term and only applies as I'd described if the warranty claim/request is raised within 6 months.
OP should by the least let us know when they purchased the 3080, and at what price so we can provide better advice. Sorry if my previous iteration of this comment gave false hope. But I still stand by the the offer of a £380 refund being insulting given the market value of the RTX 3080. given a warranty repair is possible, it isn't fair to jump to refunding that amount where they'll be very unlikely to obtain an equivalent card.
This isn't really from a legal standpoint as we don't know OP's full situation regarding the amount they paid, and the time taken between purchasing the gpu and raising the warranty claim, but moreso from a judgement of fairness and equity, where the robustness of the goods are in question, and as such there's a possible breach of CRA 2015 as has been correctly identified by Shroud below. As a consumer, buying a gpu with a 3 year warranty gives the impression of robustness, graphics cards aren't ought to fail within the first year or two, there aren't any moving parts that would cause catastrophic failure if they developed a fault. This is just my POV, from a legal standpoint, there are different arguments from both sides. But in my opinion, again provided the clauses that refer to robustness, it's unfair to call a gpu failure within the minimum UK 2 year warranty period reasonable enough to not be able to at least get a repair.
A lot of this is exactly what the others in this thread have said, I guess my adjustment of my initial method is just reaffirmation of the points made regarding entitlement to a working product and fair treatment, and I wanted to give commentary on my opinion regarding the way this makes OcUK look as a retailer.
Personally, I've been fortunate with all my graphics cards, having owned at least 6 different second hand graphics cards which have been through their own runs for at least a year each BEFORE buying, then at least another year afterwards, and I've owned 4 brand new graphics cards including my current 3070 Ti which has been serving me since July 2021 no problems. The longest running card I've now passed down to my youngest brother, an MSI GTX 970 which I've owned since 2017. Basically, in my experience I'd say that a GPU lasting under 2 years, especially a high value Nvidia xx80 card is an insult to longevity. If I have to worry about losing money on a GPU I bought 6-7 months ago, it's not worth bothering or wasting money on it in the first place....