I would like to hazard a guess that next to nobody in the southern UK will "tune" Harleys using exhaust sniffers up the pipes. ( I could be wrong of course !)
Play safe and get a 2006 specific exhaust. On my 2007 Softail Custom , ( first one into Australia !) it was the BRACKETS that were well different to the 2006.
From the side , a 2006 and a 2007 LOOKED the same , but indeed they were not ! At the time I contacted the HD dealer in Glasgow Scotland ( from where I emigrated to Australia in '95)
I had known the shop for years , back in the Kawasaki days of old.
They guided me , (and by default the Perth WA HD dealer) as to what would/would not carry over from 2006 to 2007.
All the major exhaust manufacturers are well aware for years now and there should be no problems with fitment whichever brand you choose.
You do know that , for example , V&H Big radius are "idiot loud" and will no way pass your annual MOT ?
I have V&H Big Shot Staggered on my 2008 CVO Springer, IDIOT LOUD ! , they were on it when I bought it in central Texas in 2011 before bringing it to Australia.
I have become used to them now , and won't spend upwards of a grand $AUD to replace them . Maybe that's just me haha...