My first comic? Ask me an easy one, please. I saw and looked at both Dandy and Beano when very young. Saw, because my parents didn't buy me comics. The first one I bought though might have been an issue of Super Thriller comics - these featured Ace Hart. I'd have been 9 or 10. And a year or two earlier, on holiday, I saw what I later found out was a Frew Phantom. My dad wouldn't buy it for me. I'm now 73 and a huge Phantom Phan. (But I have a soft spot for Ace Hart)
American comics weren't distributed in the UK till late '59, although I still believe there is some dubiety about the actual date. American comics turned up in Scotland because there were American bases and some obviously were liberated, finding their way into local newsagents.