All Cables grades....

CW1308 is twisted pair cable typically used for extensions and from the joint box with the outside cable to the master socket.

The others aren't twisted pair they are flat. CW1311 is four core and FCC-68 comes as 4, 6, or 8 core.

Information all directly found from google searches.

I think FCC68 is a US defined standard (FCC - Federal Communications Commission). It's a flat cable intended for use with RJ45/RJ11 type connectors. As such, it's probably best avoided for VDSL although I suspect it won't do to much harm for a short connection between a socket and a modem. However, it ought to be avoided for any extension runs intended to carry broadband signals.

CW1308, whilst originally intended for voice, is fine for broadband, although cat 5/6 will be a little better, at least for long runs.

How long before the connection fails? Multistrand into an IDC connector - not really recommended.

What makes you think it's multistrand rather than solid copper?

Probably because it sounds like a patch cable as an RJ45 was cut off. Those tend to be multi-strand so they are flexible and less prone to internal breakage when being repeatedly manhandled.

Funnily enough, the broadband socket is RJ45.

In reply to a post by MHC:

How long before the connection fails? Multistrand into an IDC connector - not really recommended.

True, but if you're only using a couple of the wires you could always tin them with a bit of silver solder prior to punching them down.