I posted this on a model engineering site and got the following response
I've used these guys in the past for work purposes
I don't know how competitve they are as price was not too much of an issue.
We have also rented containers over a period of years (when in retrospect we
should have bought) by the time we have finished with them they were looking
I don't know if philspace get many back like that and flog them on
secondhand cheaply rather than faff around pressure washing and painting.
Also the website seems to feature 20 foot ones. They used to do 40 footers
too so probably worth a phone call.
Dunno if it would help but you could mention the company I work for which is
Roke Manor www.roke.co.uk