Native cacti do OK, though I'll occasionally dump a bucket of water on some during severe drought conditions. Most non-native cacti I have on drip, along with my Agaves. Sun is back today, but here's a shady spot.
I was looking at rainfall data for where I am, in June Crieff received 3.3 inches of rain but this was spread out over 16 days! For all that the UK has reputation for rain it doesn't get many heavy downpours, just lots of light to moderate rain spread relatively evenly over time. Lowest ever monthly sunshine recorded was 36 minutes for Jan 1983 at Cape Wrath, NW Scotland.