When I re-site the CU the cable to the shower will need extending this will be a temporary measure until we do the bathroom following the kitchen. Once the bathroom is done this cable will be redundant, unfortunately part of this cable will be buried in plaster. I am hoping as it goes through the loft I can pull a few metres of new cable through. If I cannot replace the cable the join will be in an inaccessible place in the loft or buried in the plaster. Can I use crimps in either of these situations and what additional insulation do I need to use eg. heatshrink, self amalgamating tape or other?

Richard