Just an update to say not a very successful day.
The network card was not on the device settings list in the BIOS. After hours on the phone to Dell's support line, with a very helpful techie who tried everything he could to get it recognised in the BIOS so that SR-IOV could be enabled, he told me it wasn't going to be possible because if did not have the dell firmware stamp (or something like that he was a bit hard to understand). I told him that I had read on the internet that Dell disable SR-IOV on the I350 network cards that they sell, and he confirmed that. He told me that we had to buy either the Dell X520 or X540 to get SR-IOV. Guess we have no option.