I have never seen one which needs to be welded in place. I am sure they come
with the pipe already welded on, you replace the complete section.
However, if you can weld it up again, why bother with the cost of
replacement?

Hi,
I recently had the exact issue. At one end (engine) it should be bolted (I
had a nightmare with those bolts!)and at the other the pipe is clamped. I
bought a replacement from Europarts and all was good. No welds needed. The
joint towards the back was too big for the replacement clamp so I had to
use the original.
Hope this helps

Thanks for the replies, but after a lot of thought, I've had it done in a
garage today. I couldn't do the welding myself, so I ruled that out, as if I
had to pay someone to take it off to weld it, I might as well have had a new
one. It was less than I expected at £127, but other garages charged up to
£270, so it varied by quite a bit.
Looking under the car though, it didn't look that difficult, it's just I
couldn't get under the car enough with just a jack (and I didn't trust it!)

Thanks
Neil D