CV Joint problem?

Ford Mondeo Verona R reg.
In January of this year,the car failed it's MOT because of the CV Joint which got fixed by the mechanic who failed it.
A couple of weeks ago I noticed that there was a thumping noise when doing a full lock and recall this happening before.I took it to the mechanic who (fixed it) and he told us to bring it in a few days later to have a look at the CV Joint,to which I responded that the Joint had been replaced recently and had been greased up to pass the MOT.
He repaired it and didn't ask for any money as the part was still under guarantee.
A day or so later,full lock again and it was back grinding and thumping better than ever,so hubby got under the car and noticed the Gator was off and had been tied with a cable tie which had not held the boot!
Being a pensioner and with arthritis,he attempted to do the job himself,but it seems as though the boot is too small to reach the back and cover the joint.Can anyone advise us on what to do about this as the mechanic is always in the boozer and not at all helpful as I cannot contact him and complain yet again.All advise will be gratefully received if possible and hope you can help me as I need the car for hospital appointments for hubby.