The UK weather positively sucks, IMHO - too much rain!
I doubt you will be needing the bottles.
Regardless, to use them, all you need to do is fill em up, drill an 8mm hole into the cap, and put it, cap side first right into the soil near your plant.
It will leach water into the soil as and when it becomes necessary.
Again, depending on your more precise location, you may have constraints with soil and availability of light.
To combat soil issues, I would go to this grow area and excavate a hole in the ground with a volume of 5 - 10 gallons.
Start off your plants indoor, Veging for about 2 weeks under some cheap CFLs. This will give your plant that starter boost she needs.
Transplant into the hole you dug, filling with a good blended potting soil.
This will provide a more favourable medium for growth, as well as provide a good share of nutrients.
good luck once again!