What size storage container for a lawnmower?

[CharlieUniformNovemberTango]

And possibly, which lawnmower to fit it!

I live in temporary housing just now and the garden is a jungle. I need to get a lawn mower but I really can't afford to buy a shed to house it and have nowhere in the flat to store it.

I thought one of those small storage box things may work if the lawnmower would fold a bit but I have no idea on the size to get?

I've seen wooden, plastic and metal ones too so which would be best?

It will have to be lockable.

We got a keter one from tesco (using our clubcard vouchers in the exchange) that would fit a lawnmower in though you may need to remove the handle or part of it depending on the fold.