If you put a 6ft snooker table in the middle of a room how much room around the table (and how big does the room need to be) to stop you bashing the cue against the wall etc.

Around 5 ft all round.More if possible.

You would at least need another 6 foot clearance all around the table.

5ft all round from the inside of the cushions is just enough to never have a problem.
If you have a small butt for your cue or a 45 inch extendable cue from blue moon leisure,(you can get this for about £35) you are fine with 4ft all round.

A 16' x 13' room would be the minimum size needed. That would give you 5' all the way around the table.

8 ft

you will need 8ft around each side of the table

arond 6 feet

l think you will need approx 8ft from all sides of the table. As the cue stick only is 6ft tall. l just bought a 6X3 pool table and l left about 8 ft from each side.