It's great that you've kept at writing for so long! If you plan on submitting for publication, it would help to narrow your writing down to a few pieces that you like the best. Find a person or two who can read these pieces and give you their honest opinions and comments.
Take their suggestions seriously and really polish those few pieces. You don't have to be limited to a specific medium or genre, but it is often easier if you narrow your topic(s). Then, when you really feel that you've got something interesting, submit it to local publishers or writing contests (the kind you don't have to pay for).
I don't know what there is for writers in England, but I know there are lots of contests for high-school and college age writers here in the US, so I'm sure there are similar things in London. There are lots of opportunities for writers all around the world, so if you writing skills are good (judging from your question, they are better than most) you shouldn't have trouble finding a ... more.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.