Any Recommendations for Automatic Irrigation Systems for p/t, please?

Just to second this. Its important because it catches people out ...

Gardena used to have one, but I can't see anything suitable on their site any more.

Another option might be a pump on a timer. Possibly even a low voltage pump, and a car battery (and PV panel to recharge?)

 

Yes, it's one of those things that needs to work well but not of Heath Robinson style!