Posting to save someone else hours of research on this.

The bike is a SFM 125 Roadster-8A 2013
Engine = K157FMI with flat piston


-Changed the spark plug for a NGK CR8EIX (Iridium) the manual states D8RTC (but this one fits) - what was on there was a CR7E which is a hotter plug - I went by the LEXMOTO spec for SFM Roadster 8A

- You can put a CR8E on here, I went for the Iridium (IX) as a try out
- Halfords 10mm Spark plug Spanner did the job - finding what size socket was near impossible other than going in the shop and testing it!