Default [Q] Lumia 820 won't charge.

Hello, I bought a Lumia 820 a few months ago but it has just stopped charging. Last night I noticed the phone charging very slowly (1%-2% an hour) and thought nothing of it because I had it tethering at the same time. However after turning it off and going to sleep, leaving the phone to charge overnight, I woke to find the phone had only charged a little and was no longer charging. I'm pretty sure this would be covered by the warranty, but I installed the dev preview . I have very little if any money available to fix it so I have a few questions.

First let me start by saying I am in the UK for anything that may be country specific. Also the phone was new from Amazon UK

1. Is there any chance Nokia will fix it for me under warranty? If not, roughly how much will it cost?

2. Would a wireless charger still be able to charge it? I am a very technical person but I do not know if the two charging circuits are separate (until they meet at the battery) or are joined completely.

3. Is there any chance of fixing it myself? Or using a repair service? If it was a cheaper phone I would just use a repair service from a local place but this is the most expensive phone I've ever owned and I'd rather not risk it being damaged more or me being ripped off.

Thank you for your time, sorry if this is the wrong place but there was a similar topic when I made this but the problem wasn't the same.
I'm pretty desperate so any help is welcomed, thanks.
Ben.