That PSU cost about $24 US. That is low end stuff. I am amazed at how little information is supplied on UK hardware sites. The full specs on that PSU are no better than the ad.
I don't deal with any site that won't give full specs on hardware or at least a manufacturer's link. When I have found those links they STILL don't have any specs. How can a manufacturer not have the specs of a product they make?
Forgive my rant. The point of it is that you really have no clue of what Amperage is being provided on any of the rails in your PSU. Without that info it is impossible to make an intelligent buying decision.
BTW, if you have an add in graphics card and/or additional drives the PSU is most likely undersized.