Ok so its kind of resolved. I am now at 1000 mb and transferring around 20mb/sec.
Ive had to input a £14 pc world marvel 1gb card. The onboard nic, although marked as supported, is tempromental. One of those some people it works some it doesnt we dont know why. It worked on 5.0 and below, just not on 5.1, and been a newbie im not into ripping and slipstreaming drivers 
.
I tried forcing 100mb & 1000mb , it just stopped the esxi host seeing the card alltogether 
.
Thanks Andre for the info. +rep to you!
Many thanks to all who took the time to post ideas and i hope this helps anyone else in the future!