Which type of garden shed 300m from the sea?

First time looking for a garden shed. There is an 8ft mini steel shed from Adman that looks like the perfect size.

Could this be installed on the current patio slabs?

I live 300m from the sea as the crow flies. There are houses in between. Should I go for steel or timber? Or even plastic?

We do get a bit of sea spray on the windows. Would a steel shed rust? I would prefer not to have to look after the timber every year.

Thanks in advance.