Pics -
here.
Screws: 6 x 2" long Number 10 thickness should do your weight well, unless you're massive (Whether you use #10 or #12 depends on the size of the hole in the brackets - and the finishing on the hole decides whether you need countersunk (conical head, fits into conical recess), or round-head or pan-head...
Coach-bolts... four quarter-inch should do it. No harm going for 3/8 though. How long depends on the thickness of the plaster - is it Victorian? In that case you want bolts at least 3" longer than the thickness of the wood - an inch for the plaster and two in the brick. I have no idea where you get fuckoff big quarter-inch x 2" rawlplug-like things to put the coach-bolts into. Except by post from VP