Saw it on sale well under £20, incl VAT.
If the data label is the same as shown here
its got a -5v rail. And 24Amps of +12v - about as much power for a modern PC as a good 330w-350W PSU.
For comparison, SeaSonic SS-350ET has 27Amps of +12V, Antec Basiq 350W
23Amps of +12V.