I have just removed some patio slabs to put some plants on the patio to make it look more interesting, but when I have removed the slabs the soil underneath is just like a bog, can I put suitable plants in it.

Is it boggy all year round or just after it has been raining?

have you checked down under the boggy bit to see if the patio was laid on plastic instead of horticultural/permeable membrane? if its plastic you could pierce it to aid drainage or even cut out bits and improve those areas for the new plants. is it a sunny area? the world is your oyster if so, for choices of plants to break up an expanse of paving.