Homelink 75 panel – before you despatch it would it be possible for me to speak to someone for advice? My panel currently runs for about 3/4 hours and then dies. When I replace the rechargeable batteries it’s fine again and when reconnected to the psu it appears to be running from the mains supply – can these psu’s repeatedly fail over the course of a few hours under load?

I'd check the output of the psu when it's OK and when failed. That will confirm if it's the psu. It could also be overloading if something is taking too much current. Again multimeter will confirm