Well I certainly see how SOME places have dropped them in a week. Not OcUK as far as I'm aware (and I bought mine here on release day - same price now).
They have dropped one by £7

I guess they will fall more next week.
But the point is nobody is forcing anybody to buy a 4870 today.
It's called free market capitalism. Goods will find their own values based on what people are prepared to pay for them.
You can only accuse ocuk of been wrong if they aren't selling any 4870 today but clearly they are so hence there is nothing wrong with the price.
There are 20+ other places you can buy one from today if they have stock which many don't.
Equally I can find items on other etailers where the price is twice the price of ocuk but they obviously still sell some stock at that price.
Froogle any item you want and the prices will vary by 100%.
Go buy elsewhere if your not happy with the price. It is as simple as that.