Sockets on skirting board

rygon

Might be enough length but if no it will be best to change the whole length of wire rather than adding a joint box. As you are replacing like for like then it doesnt need to be Part P certified (check for kitchen tho as this is classed as a special area) but will need to be done by someone who is competent just for safety's sake

roses

I used to have sockets on my skirting until I got a full rewire done. It's more common than people think, especially with old houses. I wouldn't worry about and and just factor into the price that you will require a full rewire. Chances are it's safe, it's just old.