Is there any way I can access a bitlocker encrypted Windows 7 drive from Linux? I am not using TPM and I do have the key on a USB thumbdrive. So I have all the pieces.
You can try dislocker.
This driver uses a USB key (actually the specific .bek file on the USB drive) to decrypt a Win7 volume, so it's seem to fit your need and capacities.
There are currently no Bitlocker drivers on Linux, so that is a no.
Though, you could fire up a VM and access it from there.