I recently ran a post on shed electrics which mainly was due to
running a submain off the original consumer unit. Having had a look
at the unit i only have 3 spaces in my unit - 1) lights 2) sockets 3)
cooker. I have a separate electrical supply just above the cooker,
which at the moment only serves the boiler, washing machine and
kettle.

As there is no spare slot in the consumer unit, could i wire up a feed
from the "cooker" slot to a garage unit in the shed? or is there some
other way of doing it?