For my container plants, if the container's big enough I drill a couple small (1/16") holes in a soda bottle and half-bury it with the plants; fill it up before you go and it'll dribble for a long weekend. Maybe if your plants haven't filled out the container yet, you could put one in without damage? They're not hard to hide once the plants have grown a bit.

I tried the tiny hole in a milk jug thing and it didn't work. The water all came out within a couple of hours.

Then I tried lining the pots with sponges and that seems to work much better. Long weekends, but not a full week, though.

I also do the milk jug/water bottles with the small hole in it to water my plants in the summer. Except for one milk jug that I had buried next to my tomatoes they all worked great. It really cuts down on watering chores.

Good luck

Susan

You can try Dri-water. I've seen it at my local big-box.

Here is a link that might be useful: Driwater.com

The best place in the UK is a company called garden4less. I have added a link.

Here is a link that might be useful: Automatic Watering Systems

I prefer using a bipedal lifeform with a gardening prediliction (=a gardening pal) to water my plants when I'm gone, lol. Of course, I'm not big on hanging baskets because I never remember to water them the rest of the year! In fact, everything in my garden is watered only when first planted or transplanted, and *maybe* if it's really dry and the rain barrel is full. Otherwise, nature watering only. Not only are my water bills reasonable this way, but it saves time for toher tasks, like weeding. (Weeds always grow, even if not watered!)