hello Addick and welcome to the UK Forum.
Firstly, I use a lot of UK suppliers, iVapour, Totally Wicked being my main ones.
juice, now juices are subjective to taste, we are all different, some like tobacco type flavours, although keep in mind, that you cannot replicate the taste of burning tobacco. Others like fruit or menthol type, and as the choice is so abundant these days, you can buy almost any flavour you can think of.
I have always been a big fan of the UK produced Decadent Vapours range of juices, which these days you can get from Totally Wicked, Liberro, or e-cigz.co.uk. The first two have sub forums on ECF.
As for strengths, well, thats down to trial and error. Often when you buy your first ecig, which I dont know if you have bought one yet or not, you will receive some pre filled carts with it, and, as they often come in different strengths, will give you an idea of what strength suits you.
I started on 11mg, and then bought some 18mg, and even now 2 years later, I still use nothing higher than 18mg.
So personally I would advise a new person to start with a good ecig, such as the Ego or Tornado, a mid strength liquid, and see how things go from there..
And......never be afraid to ask questions.
There is no such thing as a stupid question.