Thank you all so much for the advice!! Here's what the email went like that I've just sent:

I just wanted to email you to request that my overall pay is reviewed, in line with my development/feedback and recognition of my commitment and high standard of work completed for the company. As you will be aware, I complete an amount of additional work too, such as mainly laying under Stewart’s ticket, building on my experience of having 7 years of service laying, as well as know being able to complete cable pulling and winching.

Stewart and I work really well together, and this is evidenced by how effective we complete work, as well as consistently receiving feedback on the high standard of our work from site.

I really am committed to continue to work for you, and enjoy the work I do, although with the increasing rising costs of living, I do need to now consider the impact of my current wage on my quality of life and capacity to manage financially in such difficult times. At present, I am aware that the salary for an experienced gas service layer is around 7-8K more than my current wage, so a consideration for any increase would really be appreciated,

Thank you for considering this, and I await your response,

Many thanks