I've finally replaced the pipe. It had a 2 inch ling split on the rear side.
I've read that you are supposed to be able to bend the pipe in order to fit without removing the inlet manifold, however I couldn't do this at all. The replacement pipe especially was very thick, no chance to bend it even when it was warmed up. I wasted a lot of time trying to work around the radiators etc. In the end I just took them out. I'd much rather pay for an air con recharge than spend several hours getting covered in oily filth!
Below is a picture with the inlet manifold removed.
There was a huge amount of oily carbon crud in the manifold. In the end I had to use a pressure washer to get it cleaned up. I ended up with a lump bigger than my fist. It's extremely hard to clean off your skin, so wear gloves. Also protective glasses if pressure washing anything.
If anyone else is going to do this, I would start by taking out the radiators, then remove the inlet manifold. I also dropped the metal pipe that the bottom of the replacement pipe connects to by a few inches to make things easier. It's a good opportunity to get everything cleaned up. Inlet manifold, swirl flaps, EGR valve and pipe, and coolant system.
Unfortunately I didn't have a set of the rubber seals that sit between the inlet manifold and the engine block as I didn't know I would end up removing it, but I would highly recommend ordering a set of them as well and replacing. All in you're probably looking at about 4-5 hours of work start to finish, depending how much cleaning you want to do.
There is one bolt on the inlet manifold that is a bit of a pain to get to. The bottom left one. It's tucked behind the alternator. Best to get at it with an 8mm rachet spanner, fed in behind the rubber pipe to be replaced. Most of the bolts you'll be removing have torx heads, E10 and E12 I think they were.
A kit that fits a 3/8 socket is best as they are fairly narrow. Also a couple of fairly short 3/8 extensions will help a lot.
The lower connection to the air con condensor is a bit annoying to get access to. a 13mm narrow socket should do it. I had to hold the radiator up a little from the normal resting place in order to get on it. Since the pipes are coming off anyway, it's probably a lot easier to detach that pipe at the other end, on the left side of the engine bay. Then remove the pipe with the radiator.
I hope that helps! Make sure you wear old/work clothes, the black crud that was coating the engine won't come out of anything. 3 days later and several rounds with some swarfega and a scrubbing brush and it's still visible in the lines of my skin. I was wearing disposable gloves inside a pair of work gloves!