Hi Vish,
I live in Cardiff, about 30 minutes from the Brecon Beacons which are the highest mountians in southern britain, they're very accessible, great fun and well marked for those starting out. I was up on the Beacons yesturday in thick snow, was quite blizzardy on the top and I was very glad to have all my gear with me. We tend to go off the cuff because its so close so if you fancy a weekend down here, let me know and I'd love to show you around. In terms of gear to start you need boots and waterproofs, a daysack and safety gear (survival bag, whistle, torch, map and compass). I always take hat and glove to the beacons, its never warm at the top even in summer. I know that plas y brenin hires out gear, but you'd be expected to have what I've put above.