I have just rewired two sockets in my kitchen to my fusebox as the current
wiring was surface mounted and I have now changed it to being flush with
the wall.

What I noticed is that the dual gang socket which we use for our fridge
freezer had the Neutral (Black) cable wired to the Live terminal in the
socket and the Live (Red) to the Neutral terminal. Before comencing the
work I checked the fusebox to see what cable was feeding the 15amp fuse and
could not see any incorrect wiring there. This dual gang socket also feeds
a spur single socket where this was correctly wired with Red going to Live
and Black going to Neutral.

What are the consequences of this incorrect wiring I have just found? Would
there have been a potential fire?

Luckily I found this and since then I have been cursing the tw*ts who wired
this up. Probably my local authorities contractors.

I know some people strongly advise that rewiring isn't something that
should be done on a diy basis and I agree to an extent however there are
certain things that can be done if you're sure of what your doing and have
looked into it beforehand.