In message , Mentalguy2k8
writes
Can you leave it submerged permanently? I've seen a lot of reviews that
praise the portability and such, but I can't find anywhere that says
you can leave it in the water-butt and forget about it.

Have you a particular product in mind? It may vary. But yes I'd imagine
they are designed to be left in the butt. Though would be a good idea to
bring them in in the winter in case of freezing.

Also, the Hozelock ones are advertised as "compatible with aquapods and
drip-feed systems", would I be right in assuming that for this to be
the case, I'd need to physically turn on the pump to feed the watering
system (as opposed to it automatically coming on for watering via
timer)?

Yes, . Though in that case a timer on the pump would be the solution to
timed operation.

Many manufacturers have manuals etc. online, which might answer your
questions, and they will have a customer helpline as well to answer
questions.

Hozelock's are he

http://www.hozelock.com/customer-service/instruction-leaflets.html
--
Chris French