Outdoor rodent shed- what features?

[Au79]

Hi we are moving house and I get to replace my garage accommodation for several cages of gerbils (two ordinary 4 shelf units not completely full) with a brand new purpose built shed!

It's going to be sited out of the sun next to the house, in London 'burbs so not too Arctic I hope. They have been happy and well in a garage with a small electric heater that keeps it from being frozen or at least too cold. But not indoors hot, iyswim

So insulation is a good idea but needs ventilation too. I want power for lights so I can see to feed and handle them in winter after work.

I want a green roof! And a drainpipe for a water butt! And and and...ok not allowed to get carried away.

What material is best? Plastic looks affordable but crappy as in ugly/not durable. Plus I want someone else to build it for me, DH will do a shite job too, but they seem to all be DIY. It's going to be very in your face next to the house so don't want an eyesore or to have to paint it.

Dream hobby she-sheds please, of the non-girly persuasion (respect to all those with hobbies though, if you like frills that's ok, but my little chaps would gnaw holes in the polka-dot curtains...).