I dont know what to say or think at the moment because whilst I was having my rear tyres swapped for new ones, I asked the tyre guy to check the rear springs (since the other garage had told me that i had a broken spring) and he could not see any damaged springs. I went under with him and using a bright torch, we inspected both rear springs - they are as good as new.
Now in the UK, we do have a legally required vehicle check called an MOT and the other garage actually failed me on 2 rear below legal limit tyres plus a rear broken spring!
I want to visit a main dealer now and get them checked then haul his ass to court if they are found to be ok.
Am back to square one - still have the slapping sound and a lighter wallet!

Watch this space