Its the nut side that I think will stand out a bit. Still an option though if the other way is too much work or I can't get the side piece out easily enough.
I don't have a picture unfortunately as it's my nephew's house. But the doors are normally marked lock or key on the side that the lock and handle should be fitted so the owner has fitted it to the other side where there's no timber between the outer skins of the door. Nuts and bolts won't...
My nephew's bedroom door handle came off. The previous owner had fitted the door handle and lock to the non key side so there was nothing for the screws to grip and eventually they all came off. Now I have a router so I can rout a piece of wood to the correct thickness to fit between the outer...
Got the tf1 omega myself, same at my parents. Bought it with the isolator valves included. I personally like it. Think I drained the whole system when I fitted it on the return pipe near the boiler.
I fitted one on my system a few years back and my systems pretty Clean with inhibitor. Doesn't collect much but the stuff it does collect at least doesn't make it to the boiler.
If the insulation in your loft is deep, maybe you've added more insulation recently, the house will be warmer but you've now made the loft colder and more likely to get condensation in there as the warm air enters the loft and hits a cold surface.