Beginner wanting to overclock Core i5-750

[King Mustard]

I'm not even sure my Asus P7H55-M SI motherboard supports overclocking (due to the "SI" part).

A standard Core i5-750 runs at 2.66 GHz. CPU-Z is telling me the core voltage is 1.152V.

Prime95 said it was running at 2.8 GHz during the stress testing. I presume this is Turbo Boost at work.

I ran Prime95 for 10 minutes, max core temps: 75C, 73C, 73C, 75C.

Can I overclock without buying a new fan/heatsink considering the temperatures above?

 

[King Mustard]

Can anyone think of an online store (apart from Play.com and Amazon) that sells coolers that don't charge £5+ for P&P?

I hate having an upper £15 budget for something, finding a product for £15 but having to pay £20+ due to the P&P.