Lag spikes on new gaming PC

Ordered and received a new Novatech PC today - stats are as follows:

6th Gen Quad Core i7 6700 3.4GHz
Corsair Vengeance 16gb DDR4 PC4-19200 2400MHz Dual Channel
PALiT GeForce GTX 950 StormX OC 2GB GDDR5
ASUS H110M-A Intel H110 (Socket 1151) Mobo
120GB SSD
1TB SATA

Fresh install of windows 8.1
Installed latest drivers for gfx card
Using wired ethernet connection

Installed World of Warcraft and CS:GO, experiencing random lag spikes (latency, not FPS) at various intervals. Tried the usual reboot, reboot router, tried ipconfig /release then /renew in cmd, still having same issues. Any thoughts appreciated

TBH, sounds like jitter, how bad are the spikes? 400ms or worse? How frequent are they as well? daily, hourly?

Much more likely to be ISP based than a problem in your setup although that’s not out of the question…

The spikes are essentially mini timeouts. Longer than 1000ms. I thought ISP related, but playing CS:GO on a laptop through the same connection worked fine.

They were happening approx one per minute.

Can be caused by very slight network or disk issues, but also drivers are a favourite.
Might be worth taking a look a the system event log, but also try running a DPC Latency Checker:
This is a very basic one: http://www.thesycon.de/deu/latency_check.shtml
This one is more advance (and far more useful). It should show you which driver is causing an issue (if the issue is indeed DPC latency): http://www.resplendence.com/latencymon
Once you know which driver may be causing an issue you can try reinstall or update it.