Excessive Daily usage for one day ONLY

[#1]

Hi all,
I am trying to narrow down a large excessive bandwidth usage on my account.  I have spoken to support (A very helpful person called Simon) and we couldn't seem to resolve the issue.
Our normal daily usage is around 1gb per day (not counting overnight usage), some days (Like when the ME3 Extended Cut, or the GW2 Beta event weekend,; or pretty much anything gaming related happens) our NET usage will go up.
This morning, we have a 1.94gb usage and I cannot work out what on earth it is.
I have a few questions:
1. For this month (which is about 1 week) 4% of my net usage is for Usenet, but I don't use Usenet at all, are there any other services, RSS feeds, for Google Drive ,Reddit website, that are classed by your traffic shaping as Usenet?
2. I have a NAS drive that I have connected to the local network (recently purchased ZyXel NSA310) and since the media server on it is very poor (almost crap) I decided to use Serviio as the media Server, does anyone know if either of these have features that would cause excessive bandwidth usage?
3. What services do you class as streaming? Is this iPlayer, Youtube? We have a high percentage of Streaming overnight, but we're in bed, I would use that time to download XBOX patches, games etc. Are patches and downloads for XBOX games etc classed as Streaming?
Any help and feedback would be very much appreciated.
Best Regards
udoh.

[#2]

The only thing I can think as a possibility is that Serviio is caching a chunk of data.
Have you checked the cache size

[#3]

@Oldjim Thanks for the reply, I have checked the cache files and they don't appear very large. For now I have shut down the NAS drive and stopped Serviio, but what I don't understand is why Serviio to a LAN NAS drive would send large amounts of data across the internet.

[#4]

Could it have been something updating? Failing that, serviio updating the metadata for all your media that's on there? I don't know anything about it I'm afraid so am not sure if it does this, but it could do - and if you have a lot of media and it gets sufficiently high resolution cover images that could be up to a gig I guess?

[#5]

@MattTaylor It's what my gut is telling me at the moment, can't quite work out why it decided yesterday was the day it wanted to do this, never before, but for now most things are off and i'm checking "one by one".
Does anyone know the answers to question 1 & 3 with regards to the traffic management questions?

[#6]

SKY Anytime+, or another Internet based service, such as BBC's The Space ?
I have Anytime+ connected via ethernet into my router from my SKY+HD box, and BBC (and other) interactive services via ethernet into my router from my Freeview HD box, and Freesat HD box too.
These are not recorded on my computer, but obviously PlusNet record all usage through my router and Broadband connection.
Just a thought.