AsRock B75 Pro3-M (good audio codec, SATA3, USB3, PCIE3 with IvyBridge; NO OC though) £56
http://www.amazon.co.uk/ASRock-B75-Motherboard-Instant-Charger/dp/B007RQ0HSA
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i5 3470 (i3 3220 would be ok, but i5 is more future proof - 4 physical cores) £146.98
http://www.amazon.co.uk/Intel-I5-3470-Processor-3-20GHZ-Socket/dp/B0083U94CO/ref=sr_1_1? s=computers&ie=UTF8&qid=1354129745&sr=1-1
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Sapphire HD7850 2GB GDDR5 (good cooling, good GPU OC) £155.00
http://www.amazon.co.uk/Sapphire-11200-07-20G-Graphics-HD7850-GDDR5/dp/B008HV63NM/ref=sr_1_4?s=computers&ie=UTF8&qid=1354129866&sr=1-4
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Corsair TX550M (very good PSU, detachable cables for beter airflow) £56.38
http://www.amazon.co.uk/Corsair-TX550M-Enthusiast-Series-Modular/dp/B005DGEMKK/ref=sr_1_1?s=computers&ie=UTF8&qid=1354130191&sr=1-1
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Fractal Design Core 1000 (good small case, very good airflow, but only 3 HDD bays) £34.28
http://www.amazon.co.uk/Fractal-Design-Core-Series-Micro/dp/B004ZH18G4/ref=sr_1_1?s=computers&ie=UTF8&qid=1354130255&sr=1-1
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Corsair Vengance LowProfile 8GB 1600MHz 9-9-9-24 (low profile memory, more room for airflow) £32.47
http://www.amazon.co.uk/Corsair-CML8GX3M2A1600C9-Vengeance-1600MHz-Memory/dp/B00569K7LM/ref=sr_1_3?s=computers&ie=UTF8&qid=1354130420&sr=1-3
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WesternDigital Caviar Black 1TB 7200RPM (good drive) £74.86
http://www.amazon.co.uk/Western-Digital-WD1002FAEX-Caviar-Internal/dp/B0036Q7MV0/ref=sr_1_8?s=computers&ie=UTF8&qid=1354130549&sr=1-8
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TOTAL: £556
you can go with i3 3220 to save about £60
In general I wouldn't go with AMD CPU. They lack in performance compared to Intel and AMD's efficiency is waaaaay of.
Intel's B75 chipset is a good cheap option if you don't plan to OC the CPU (the same performance as Z77). GPU and RAM OC is still possible though.
I have the above components so I know what I'm talking about. My PC runs cool and silent - CPU max temp during 4x 100% load is around 70°C, GPU max temp during 100% load is around 69°C (fan is set to 40% so its completely silent). The only thing I hear is the main fan which is only audible if your room is silent.
good luck!