you should be able to remove the lower pas bracket and then undo the 2 pivot bolts and 1 tensioning bolt for the pump. this "should" then pivot out of the way enough.
however on mine the big bolt that holds the lower pas bracket to the upper bracket was not in the mood to move so i removed all the pas pump bolts and cable tied the pump to the front crossmember.
then i removed the alternator and the upper and lower brackets together.
this will give you access to the thermostat housing. undo the two bolts and remove.
refitting is reversal etc............
i have heard that it can be difficult to get the new stat and housing to seal properly and the only way you are gonna know is to connect it all back up and run the engine till hot!! get a new housing and seal and bolts just to make sure.
i was lucky, mine did not leak.
it may be a good idea to replace the water pump while you are there. if you are gonna take it all off, why do it twice?
the water pump's are only £25 ish from GSF - get a berut one, they are same as the dealers.
good luck!!!!!