Storage (not car related)

I'm opening a gym next year, and will be buying some kit mid December. Too good a deal to miss, literally saving me 10s of thousands (couldn't afford to do it without this falling at my feet).

The kit has to be picked up mid december, but the plan for the gym is to open up next summer ish.

I need somewhere to store this stuff, and the big commerical storage places are coming in at around £72 a month - something that whilst not astronomical is an expense I'd rather minimise as much as possible. The kit is weights, racks and matting so no big treadmills or such like.

Anyone have any suggestions?

Place near me does 40' containers cheap. Outdoor, but a secure yard. Used to keep my Winnebago there, near J37 M62. Nothing to do with me, but a cheap option perhaps.