So I bit the bullet and changed the water pump. Don't particularly like ticking time bombs
It turned out that the old one had a bit of play on the bearings. The plug which allows to drain coolant from the engine block looked like it would break as soon as I even thought about removing it. I figured I'd rather wipe the coolant off the engine than fight the plug, so I just drained the radiator and let the coolant from the pump and the head leak out when I disconnected the pump
A bit messy, but not too bad. The old O-ring (between pump and the block) was a bit difficult to remove, after 230k kms it looked nothing like rubber, more wood. After poking it for a while with a small screwdriver it would eventually come out, but access is a little awkward. Cleaned the groove, new O-ring, this is a must, reusing the old one is really begging for trouble. I reused the gasket between the water neck and the head though. It looked allright and seems to be holding so far.
New timing belt, tensioner and she purrs like a kitten.
It is quite tricky to actually remove the water pump assembly from the vehicle because power steering pump is in the way. I had to unbolt the PS pump completely, except for the hoses fortunately. This allowed to move the PS pump towards the firewall and push it down a little, so that the water pump could come out along with the neck.