This is due to a centre bracket rusting prematurely and breaking off the exhaust, either both sides or just one side of the centre section where it attaches to body in the 'caged' section (dead centre under the car).
I checked mine and sure enough, one side of the bracket after the CAT and centre silencer was rusted through and the exhaust had dropped.
VW have seen it many times and they fix it by putting large jubilee clips around the exhaust and bracket so it holds the exhaust up again.
Apparently, VW Golf's also suffer from this and jubilee clips are used the same way.
Anyway, it's fixed for now and MOT'd anyway.
