I would urge you to buy 2nd hand. Look for bikes being sold locally on ebay and don't be afraid to ask if you can go and see the bike. Its in a sellers best interest to agree as it gives a better chance you will bid. Amazing bargains on road bikes are tougher to find than some other bikes, they do however exist if you look hard. Bikes costing less than £400 new, tend to be poorly made and use the cheapest components available. A poorly made aluminium frame is potentially dangerous as aluminium cracks rather more catastrophically than steel and cheap components will tend to go wrong.

I have also answered one of your other posts about the frame you have. I bought the same frame but with all the shimano 105 golden arrow components not stripped (or the fully working ready to ride bike in other words) for just over £150 off ebay.