Welcome to ECF!
I dropped by to say I was being a dumb American tourist in Newcastle not all that long ago. My father went to uni there. I'm honestly surprised to hear vaping pick up there, as when I was there last year, there was no one vaping. Well, then again, the area's got a nice river breeze, wouldn't be able to see any big clouds wafting from the nearest coffee place...
As for DIY juice, experimentation gets you to perfection. PG/VG ratios, the PG/VG base to flavour concentrate ratio which changes per flavour, nicotine strengths, etc. Everything can be perfected through experimentation. I made 2 batches of DIY mango-banana-strawberry-kiwi, with all the same ratios. Somehow, one ended up great, and the other came out horrible and nasty. I'm a noob at diy juices too.
Cheers!