Hi
@Haris19 I do not think you should be worried about A-level grades. Firms have always cared a lot less about A-level grades than about university performance, simply because what you do in the more mature and difficult university setting is more relevant to assessing your potential from an employment perspective. They do not expect you to have always have a flawless academic record, and being able to show you have had struggles but managed to overcome them and then excel is certainly an attractive trait. Also, the trend of firms not placing much weigh on A-levels has accelerated recently, with many firms significantly lowering or dropping GCSE/A-levels requirements completely. Even those that have kept them in practice tend to treat them more as a 'soft expectations' than a mandatory field, as there are many examples of forum members who did not meet the A-level requirements of Magic Circle/US firms, but chose to still apply and ended up getting TCs.
In your particular context, considering the very high overall first at a reputable university and the impressive postgraduate degree at Oxford, I honestly cannot imagine any firms would reject you on the basis that you did not excel academically in a much less difficult context several years ago. As such, I don't think this is an issue that should cause you any concern or impact your application strategy, besides perhaps not prioritising applications to firms that have requirements and (all other things being equal) preferring to apply to firms that do not.