1. Grab an overclocking guide specific to your board and "go to town". Start at say 4.2 and work ya way up.
2. As for best boards for overclocking.....I always seemed to have better luck with Asus, although to my mind (and most reviewers) MSI has made a great push into the $150 - $220 market (particularly the GD-65 and G45) starting with Z77 where they compete well with Asus, though I think they currently provide a bit more value in this segment. I have had no issues with Gigabyte which some of my users seem to like cause they have a specific color scheme they going for.
3. Personally, I see no value in the ALC coolers. If I'm gonna put water in my system, it's gotta give me significantly lower temps and significantly lower noise than the better air coolers.... no ALC unit accomplishes this. However I do understand that some people have an aesthetic objection to "big iron" which overcomes the noise factor.
Is your £700 budget for an entire system or just the MoBo / CPU / GFX ?
I'm gonna make one change tho ..... With Z77 Mobo models rapidly disappearing from the market as existing stocks sell out, I'll echo the comments of this reviewer
http://benchmarkreviews.com/252/msi-z87-mpower-max-motherboard-review/12/
I don’t think there’s any compelling reason to move from an Ivy Bridge or even a Sandy Bridge based system to a Haswell system– there simply isn’t enough performance and feature differential to justify it. On the other hand, if you’re building a new rig from scratch, there’s little point in investing in end-of-life platforms, so going Haswell/Z87 makes sense.
GFX Card - MSI GeForce GTX 770 Gaming Edition £321 w/ VAT
http://www.scan.co.uk/products/2gb-msi-gtx-770-tf-gaming-pcie-30-%28x16%29-7010mhz-gddr5-gpu-1098mhz-boost-1150mhz-cores-1536-dport-dvi
MoBo - MSI Z87-G45 GAMING £120 Inc VAT
http://www.scan.co.uk/products/msi-z87-g45-gaming-intel-z87-s1150-ddr3-msata-sata-iii-sata-raid-pcie-30-%28x16%29-d-sub-dvi-d-hdmi-atx
or
Asus MAXIMUS VI GENE £158
http://www.scan.co.uk/products/asus-maximus-vi-gene-intel-z87-s-1150-ddr3-sata-iii-sata-raid-pcie-30-%28x16%29-hdmi-matx-plusfree-deliv
or
MSI Z87-GD65 Gaming £153
http://www.scan.co.uk/products/msi-z87-gd65-gaming-intel-z87-s-1150-ddr3-sata-iii-6gb-s-sata-raid-pcie-30-%28x16%29-d-sub-%28vga%29-dvi-d-a
CPU - Intel CPU i5-4670K 3.4GHz £184
http://www.scan.co.uk/products/intel-core-i5-4670k-s-1150-haswell-quad-core-34ghz-38ghz-turbo-1200mhz-gpu-34x-ratio-retail-plus-fre
The Gigabyte Windforce has the same GFX card clocks as the MSI version which is higher than the Asus and EVGA models. The Asus and Gigabyte boards in this price range are also just fine and all have similar RMA rates, but neither has the MIL spec components, nor number of awards in this price segment.
While IB overclocks 6% better on average than HW, HW starts out 10% faster outta the gate so it never quite catches up. And with replacement parts getting scarcer for end-of-life components, I have a hard time recommending end-of-life 1155 socket components on new builds
Read the reviews, compare the feature sets and pick what fits ya needs the best