Wow. Thanks for bumping this as I hadn't seen the original posts. The pics in the OP sent a shiver down my spine. I can remember seeing a Comic Showcase ad in a Marvel UK book in the early 80's and not quite believing that such a thing as a shop selling only comics could possibly exist. I begged my mum to take me into London so I could go there. Eventually she relented and come the school holidays she took myself and my best friend into town. I had managed to scrape together the princely sum of £20 (a fortune to me then). Mum dropped us at the door, said she was going for a coffee over the road and would be back in half an hour or so. I can still remember the sensory overload as I walked in; the smell of old paper, the thousands of brightly coloured covers staring out at me - I was literally in heaven.
But what to buy? my fortune now seemed woefully inadequate as I wanted, no needed everything in the shop. Unfortunately, I was seduced by the racks of recent imports as I had only ever obtained new comics from poorly stocked newsagent spinner racks or once or twice by mail order from companies such as Dangerous Visions, (great fun trying to get my dad to write a cheque made out in that name as I handed by pocket money over to him!). From memory I bought a huge stack of newly released Marvels. I did buy a Fantasy Masterpieces because it looked so ancient!
Of course the half hour was over all too soon and we were off. I do remember there being an old man with a market traders cart around the corner from the shop which was half covered by old comics and half covered by soft porn mags (my pubescent mind literally exploded!) from whom I bought a Hulk Treasury edition for a few pence.
A wonderful memory and I still have the Comic Showcase carrier bag with the Joker on it somewhere. Happy days...