I don't really know much about overclocking, so I wasn't factoring it into my plans. I'm a bit wary of messing with stuff I don't understand. How simple is the whole process?
Don't worry about it, in your budget you can get a decent i5 and it'll far outlast this generation. Besides you can easily clock graphics cards these days from the software they install. You can get pre-built cpu/motherboards, my latest one was a deal for an i7 overclocked and it turned out just an extra £50 than the parts seperately and is under warranty.
As for SSD, unless you plan on getting a massive one to install games onto, it's not a necessity. I myself haven't bothered, I pumped the extra money into a decent hdd and the extra system memory. If you look into optimising your computer for your needs, the windows boot time and all that isn't really an issue. SSD's are great and are the future, but really not worth the cost at the moment compared to the other components.
For games you really want to look at memory and graphics cards mostly anyway, as even a low i5 or a top i3 will easily compete with anything this gen throws at it coupled with a decent gpu set up.