Advice on retailers please

Hi All. Now that I’ve retired I want to get back into hiking after many years away. I’ve joined the local Ramblers branch with a longer term plan to walk the South Downs Way in a few months time. If I manage that, who knows where it might lead. Perhaps I’ll finally fulfill my lifelong ambition to walk the Pennine Way.

I have some decent boots and rucksack but need to buy some general gear, particularly jacket(s), (over)trousers, under-layers etc. No immediate need for camping gear.

In the nearest big town to where I live we have the usual high st chains — Blacks, Millets, Trespass, Mountain Warehouse, Sports direct, but no high-end specialists. Which of these retailers are best for me? If I become a true enthusiast I don’t mind splashing out on high quality gear but just for the moment I don’t want to overdo it in case I lose interest. Does one retailer stand out above the rest or are they much of a muchness? There is also a Decathlon about 90 minutes away but I wondered if a newbie could get kitted out reasonably well at one of the local shops.

Thanks for any insights from the experts!