Author has written 12 stories for Harry Potter.
I've been on the Harry Potter bandwagon since about when Goblet of Fire came out, but I wasn't inspired to take up fan fiction until I read Less Wrong's excellent Harry Potter and the Methods of Rationality and started exploring from there. (Okay, I did a little Star Trek years and years ago, but it was so bad that I don't even want to think about it.) I've been seriously working on original writing for a number of years, but I like the ready-made framework and low pressure of fan fiction as a way to write faster and improve my craft quickly.
I find it fascinating how new ideas are developed and propagated through the community, from fleshing out background characters (e.g. a lot of the Slytherins) to inventing whole new branches of magic (e.g. warding). This can cut both ways, as with the overused Evil!Dumbledore, Evil!Weasleys plots, but it's amazing how it enriches the shared world of Potter fanon.
In my own writing, I'll often use these elements from fanon, especially if they make more sense than JK Rowling's original, which happens often--using Arithmancy for spellcrafting, for example. But I use them judiciously. I try not to go out of character, at least not without showing how different events caused the characters to change from canon. I rarely go fully AU and change the actual rules as set down by JKR, and I try not to include anything story-breaking.
On the other hand, many of the common tropes of fan fiction are overused and poorly thought out--things like wizard's oaths, time travel, marriage laws, character bashing, and worst of all, super!Harry. Too often, these plots are just lazy ways of solving Harry's problems, fixing the mistakes of various characters, or getting your favorite couple together without giving the story or the characters the thoughtful exploration they deserve. That's why, when I draw on these tropes, it's usually for parody, or else a deconstruction and reconstruction to show how it should realistically go.
On pairings, I don't have a stake in any particular one. I care a lot more that a couple is well-written (and halfway plausible: I'm looking at you, Hermione/Snape) than about who is in it, although slash isn't my cup of tea. I will say I have a soft spot for Harry/Luna, though, and I highly recommend Arpad Hrunta's stories if you are interested in that.
I'm not British, but I write my stories with my computer set to British English. I know it's a little inconsistent, so I apologize for any linguistic mistakes.
Current works in progress:
The Arithmancer: Full-length story where Hermione is a mathematical genius and becomes a brilliant spellcrafter. Explores Hermione's struggles with the stress of growing up and frequent brushes with death as she develops into a powerful witch. Features in-depth exploration of magic and a strong bond between Hermione and her parents. Updates every Saturday.
The Accidental Animagus: Full-length story with Harry as a cat animagus who was raised by the Grangers as Hermione's brother. Features Harry with a strong support structure, Wizengamot politics, and characters acting rationally. Updates every second Saturday.
Petrification Proliferation Novella-length story about what would happen if the basilisk were treated like the weapon of mass destruction it is and the consequences of what would happen if everything was carefully investigated from there. Updates intermittently.
Future planned stories:
I don't want to make promises I can't keep, so I can't say much for certain. I can confirm that I'm working on a novella-length companion to The Accidental Animagus showing different forms of magic and magical cultures around the world.
Beyond that, I have plans for several one-shot stories that I'm reasonably sure about. These will be parodies or deconstructions tackling marriage laws, soul bonds, the standard super!Harry-plus-Weasley/Dumbledore bashing plot, and time turners.
I have a lot more ideas, but I don't know if any of them will see the light of day, so I'll leave it at that for now.