i have an automated system in the greenhouse. it was easy to set up but it will use a lot more water than the cans will. so if on a metre I'd imagine it will be more expensive. set it to come on in the late evening if you do go for it as you will lose less water by evaporation.

in the height of summer the greenhouse one comes on at 4am for 20 mins and at 8pm for 30 mins. this is what we found suited the plants best.

what plants is it you are watering PDB? once established they should need very little extra watering.

Thanks SBG I was thinking my borders. As we seem to be spending hours at night watering them at the moment. I have rather a lot of annuals and so they need watering until established. But you are right in as much as once they get going we really don't do much to them. I will have a rethink . Thanks again

You could get a few more water butts, connect them in series and use the water for your water supply. It will save you money and be more beneficial to the plants as rain water is always better than tap water for plants.