Can anyone help with my Blu-Ray?

[chunkymoonkey]

Hello everyone.
I am new to this whole forum thing, but I am need of some help.

I have just recently bought a HD TV and a Blu-Ray player.

Samsung LE46F86BDX (Full HD 1080)
Sony PS3
Sony STR-KS 1100 (Surround Sound)

I bought both of these items because here in the UK both products have won numerous awards for quality of picture.

My problem is that sometimes the picture quality is really poor. When I am watching a Blu-Ray movie and the picture is bright i.e daylight is looks amazing. However when it is dark it looks pretty shocking. It does not look much better than old VHS. Its really fuzzy & grainy. Its terrible. I am a Sci Fi freak, so much of the Blu-Ray movies I have are pretty dark.
Now the weird thing is, when its black it looks great. Its all the shades around black that are the problem. Grey, dark blue etc.
I have set the PS3 to play at full 1080.

Its really doing my head in so any thoughts on what I can do I would really appreciate. Thanks for your help.

Christian