So sorry for the late reply with this one. The issued turned out to be the universal joint between the intermediate shaft and the steering rack as first suspected. It was pretty badly corroded. My mechanic has greased it up and it works perfectly now. I think he used penetrative oil the first time which wasn't enough to solve the problem. The grease however has worked a treat. I'm under no illusions it will need replaced at some point as the grease is only a temporary fix. There are a few videos on YouTube of people saying they grease it every six months or so.
Thank you all for your suggests.
