To repair damage 13 amp ring cable can I use a flush fit DP or should I use a 30amp junction box which would be surface fitted sticking out like a sore thumb. Or Crimp joints in to a plain flush box.its a feed to sockets.
First of all there is no such thing as 13A cable. Cable is referred to by its size, which in your case is probably 2.5mm.
Any junction box used must be accessible, how ever if you use the correct size crimps and you have a ratchet crimper these are an acceptable alternative. You may also want to look up "wago connectors" and "wago box" as these are considered to "maintenance free" so in theory once you have used them you can cover them with your choosing.
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