iPod Internet provider blocking iTunes?

For the last few weeks I haven't been able to access the iTunes store, app store or even apple.com during peak times of the day. My iPad and iPhone can access all sites ok, and are routed through the same Airport, so it seems odd, but could it be that my internet service provider is blocking regularly visited places in peak times?

Is there any way to check? I've done a speed test and its slow (5Mb) but there, and some sites (less frequently looked at) are ok. Or do I have a cache problem somehow? (Have reset Safari)

Just wanting to buy some movies...!

Thanks in advance for any help, Niall