Roughly 500W PSU with LONGEVITY in mind

[tamethegamer]

Looking for a semi or fully modular but trustworthy PSU to power this ITX build:

https://uk.pcpartpicker.com/user/kierangooodson/saved/#view=xMQnTW

I'm assuming 500W should be enough.
The case supports ATX sized PSUs.
What do I get?

 

[Dark Lord of Tech]

Full modular made by SEASONIC.

PCPartPicker part list / Price breakdown by merchant

Power Supply: EVGA SuperNOVA GS 550W 80+ Gold Certified Fully-Modular ATX Power Supply (£64.99 @ Aria PC)
Total: £64.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-10 02:40 BST+0100

 

[IntelTurtleFan]

The above poster beat me to it. That is exactly what I would recommend 100000%.

PCPartPicker part list / Price breakdown by merchant

Power Supply: EVGA SuperNOVA GS 550W 80+ Gold Certified Fully-Modular ATX Power Supply (£64.99 @ Aria PC)
Total: £64.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-10 02:42 BST+0100

Another good one very similar to it is the XFX XTR. Both are of highest possible quality.
PCPartPicker part list / Price breakdown by merchant

Power Supply: XFX XTR 550W 80+ Gold Certified Fully-Modular ATX Power Supply (£68.23 @ More Computers)
Total: £68.23
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-10 02:43 BST+0100