You can't use a 'choc block' as it is not maintenance free. (And you wouldn't fill straight over an electrical connection.)
You either need crimps and heatshrink over it.
Or wagos in a wagobox.
Or solder and heatshrink.
Soldering is a pain unless you know what you are doing.
Crimps take up little space, but you need the right sizes and a DECENT crimping tool, or they will come adrift. They will need to be sleeved with heatshrink sleeving or placed in a suitable enclosure.
Wagos are incredibly easy, but the rule is they have to be placed in a wago box when inaccessible. This means digging out some of the wall to accommodate it, but they come in various sizes. When I say wago, I am of course using a brand name, and should point out other brands will be available.
Hence why I was keen to replace the cable in the wall and do the joint in a ceiling/floor void, if there is one.
Send a picture if you can.