As long as the end effect of the design was what you wanted/looked nice there is nothing wrong with that no.
If you feel you would benefit from further training, have a look into it and go for it! Or if you don't quite need hands on help try buying the Lash Bible volumes or other books of that nature!
LieLash did some helpful tutorials for already trained techs if you search 'eyelash extensions in kent' into YouTube...
Do your clients know that £30 is just your introductory price? If not then start putting on your things that it is an introductory offer.
Always hard to tell from photos but the lashes look nice and separated and full from what I can see. I wouldn't worry if I were you!
What does the girl who does your lashes charge? And what diameter/length/curl extensions does she use? (I know it seems odd/nosey to ask)
And yay! Hope you like it!
Have a look into buying some masks with respirators btw (there's some on LashBase) all lash techs ought to wear them so we don't over-expose ourselves to fumes