hi got advisory on my 09 plate Mondeo says n/s and o/s rear trailing arm bush worn now can u just buy bushes or has to be complete arm and what does this part look like looked on ebay shows few diffrent ones any help would be great 

You can get bushes separately. You need a special bush remover/fitting tool 

+1 for what @iantt said, a "decent" garage will have the adapter kit which means they only have to drop a small part of the rear sub frame rather than the whole lot i.e. taking the rear trailing arm out.  You also want to be fitting a decent brand bush e.g. First Line, no "Chinglish" parts of ebay.

Bushes are about £25 each for a decent brand. I bought Ford parts when I changed them on my car in May this year. The tool is about £130.

The reason I changed them myself was that the local Volvo specialist (same as the V70 and S80's I think) wanted to charge me £400 and the Ford dealer, who quoted for less than £200, didn't actually have the tool.

Once fitted I had a full wheel geometry done and all has been fine since. The rear tyres had worn unevenly and the worn bushes caused handling issues like understeer and then oversteer on bends/corners.

Suspension can be mostly left in place when doing them