I have a 160 thermostat and a fan controller that keeps it at about 175-185 in all weathers (its a daily all year round). Not got the bottle for this 230deg stuff after my fan failed one time and it hit 260 in an instant! I like some warning of impending doom! Been that way for 10 years now, without any problem.
For flushing, I backflush when I can, and use a crushed dishwasher tab to clean it out before I refill.
My radiator cap is one of those ones with a lever so I can burp out any air safely.
Tips..
When fitting a new thermostat, bore a couple of 3mm holes each side of the flange to allow air to pass to the top of the radiator.
Leave the block plug and knocksensor in place or you might find it and its threaded hole, will crumble.. Let sleeping dogs lie.