Actually, the first to die will be the ones at ground zero

And you don't get to choose where the asteroid hits, so you can draw what comfort you can from that
Welcome to the forum. You could be an interesting case. In order to acquire skills in survival techniques, are you prepared to accept a level of discomfort at least comparable to your camping experience? One can read about staying warm and dry, making fires in wet weather and finding/building shelters, but until you have done them in at least somewhat uncomfortable conditions you won't fully appreciate what you have read. Knowing that you can do things in less than ideal conditions, knowing that they may be harder than the books make them sound, because you have done them before in those conditions, will help a lot with your mental fortitude, which is probably the biggest factor in survival.
Having said that, if you stick to the UK you can survive just fine with some extra warm clothes, a blizzard bag, some cash and cautious approach to hiking alone.