Found a place (via ebay) in Redditch who will custom make me a straight through centre pipe out of stainless and fit it for around £50, which seems like a steal to me.
I may also get them to swap the downpipes while it is on the ramp as I think these are knackered as well.
Will prob be a couple of weeks before I sort this but will post back with information on what they're like if anyone else needs this sort of stuff doing.
M