Heat pump 0.5 bar is it plumbed correctly

Hi I've bought a house and I'm not sure if the heat pump is installed right. Heatpump is from the last 4 or so years.

It's at 0.5 bar, the one hot tap beside it has high pressure and the rest are very low pressure.

It's getting cold mains through a tank in the attic, and the way it's plumbed I'm not sure how to add more pressure or if it's possible to add more pressure without changes including another expansion tank and taking the attic tank out of the loop.

I would have thought the silver braided line should be going to mains cold and be left turned off except when adding pressure to the system but it is as it is in the diagram, and it seems to be with the valves open.

I don't have the expansion vessel as in the top right of that diagram but I have the one on the left.

Does it seem like it's wrong and I need a good plumber in to look at it?

thanks