Can fit a several boxes/bags of stuff. Currently its my spare room, where I have a desk in it for my work, and also acts as my dryjng room for my clothes (I have a dehumidifier).
I don't use this room enough at the moment., but theres two closets/storage cupboards inside for my own personal stuff.
My house has a monitored alarm system (I get phone calls if the alarm is triggered) and I have a camera in the house too.
Front and back patio door locks are both multi-point lock, so it's very secure.
Ideally you'd drop off your stuff and then get back in touch when you want to arrange to collect them, thought depending on how long your stashing your stuff here (if longer term) then visits may be allowed from time to time.