i looked for some psu's around £25 and i narrowed it down to the cheapest best two that i thought had the best reviews and overall quality for that money. they are both around 40$ which is right around £25.
also, as for your current setup you'd be using 2 sata connections and idk if you plan on adding any more sata hardware i.e. hdd's
this one is 450W, but has 2 sata connections, 1 pcie. bonus: all the wires are wrapped in mesh for cleaner look and less mess.
Newegg.com - Rosewill Stallion Series RD450-2-DB 450W ATX V2.2 Power Supply - Power Supplies
this one is 500W, has 4 sata connections, 1 pcie
Newegg.com - COOLER MASTER eXtreme Power Plus RS-500-PCAR-A3 500W ATX12V V2.3 Power Supply - Power Supplies
again, these are just suggestions. cheers