Shipping containers are wonderfully solid and secure, but add nothing to the value of the property. They're a cheaper option than a traditionally built garage. You can get a car into one, but it would be a struggle to get yourself out of the car.
The other thing is Planning Permission. Garages can come under "Permitted Development"
https://interactive.planningportal.co.uk/detached-house/outside/garages
Even if you needed Permission, you're much more likely to get it for a traditional block.
More importantly, "Permitted" is usually for private use only. If you rent out, then you would need to apply for "Change of Use" PP.
I know people do it on the quiet, but it only takes one "concerned neighbour" to report it.
So, I reckon go for PP "business use" for a little block of regular garages. They're always keen to see parking and/or storage. Good "added value" to the house as well.
Listed Building/ Conservation Area/ living next door to Buckingham Palace might make the PP more difficult though ;o)