Why would you not overclock an E4x00? The things overclock really well even with the stock cooler and voltage increase. Get an aftermarket cooler like an AC Freezer Pro (cheap and with good performance) and you can save getting a more expensive CPU. Got my E4300@1.8 up to 3.4 with basic water, and 3.0 with an AC_FP.
Go for more like £45 minimum on the PSU. You should be able to get a good quality one for that, and all the other components will thank you for it by not crashing as often/burning out.
Yeah, my E4400 does 3.33GHz on the stock HSF, I've had it at 3.4GHz @ 1.45V for benching but it gets too hot for my liking, I'm sure with a better HSF I can do 3.5GHz.