Had something similar here in Ayrshire a couple of weeks back, a thunder storm that just sat overhead for about 5 or 6 hours, nice bit of flash flooding too. Came without warning too, didn’t feel like a thundery day, I was out watering my pot plants a few minutes before it started, worrying they were going to dry out, half an hour later I was trying to stop them floating away
Yeh I’m also from Ayrshire although the thunder and lightening we had only lasted 3. Just got back from my ride home and it started as I put the bike away. Never seen a storm last that long.