4mm spliced to 3mm wire ok for uk plug socket? See pic

I am upgrading an old socket in my kitchen.
The new plug has the ports in different places and now one of the live wires is too short.
I got some splice connectors and used some cable I had left over from a cabin build which is good quality and I didnt notice until I spliced that the existing cable in the wall is approx 4mm diameter but the cable I used is approx 3mm. (This is the width of wire and insulation)
Will this be ok? I'm impressed with the splice things they are very solid.

 

The Distance is negligible and will make very little difference resistance wise. Can't see a Grommet where the cable enters though.

 

I've added a picture, let me know if it helps.

 

The Neutral needs tucking in more but other than that should be fine

 

Will do, thanks