Staffy, if you were closer to Melbury Motors, my staff would be at your disposal to give you an honest opinion of what's wrong, however the distances involved here would make this a hugely impracticable exercise.

I'm afraid to say that if there's no one on here close to you that can have a quick look at it with you, then you're into a garage to make a definitive diagnosis, some may charge for this, some may not.

I feel that it is an essentially simple problem, Mondeo's being Mondeo's are (generally speaking) cheap & easy to fix, with several know culprits that cause problems, lower arms being one of them, there are a few others of course, it is never as simple as all that!
Hopefully there is an honest garage close by that can be of assistance to you & not go down the "sell up" route.

If I can be of any further assistance in this matter Staffy, then please do not hesitate.

Melbury.