If you look at the cable on the right, you can see it comes in at the bottom but, you can the bare cable pocking out the top, hence there will be two screws tightning each cable down!
You could replace the existing with a 4 way earth block or use another earth block for your gas and water, using the existing blocks gas bonding connection to connect the two blocks together.
This is typically all you need or you can use a henley block £7.60 also available from screwfix.
https://www.screwfix.com/p/ced-4-way-earth-block/12386