I know there are plenty of guides online on how to change the cam follower, but I didn't come across many outlining the differences when you have to tackle a banjo bolt fitting (just a lot of moaning about how awkward it is!)
I went through the usual steps of removing the engine cover, and noticed my HPFP had 2 metal lines underneath.
I didn't have a mirror to hand, so stuck my phone in, looking upward (photo taken after I'd removed the first fuel line)
That'll be the M8 triple square. Luckily I had a set in my kit (needed to remove the front seat mounting bolts)
One of the online guides suggested removing the HPFP fuse and starting the engine, which would cause the pump to depressurise. I checked some wiring guides online, and found the #27 fuse (the blue 15a I'm pointing to...took a photo so I didn't return it to the wrong location!)
Removed the top sensor from the HPFP first, started the car for 10 seconds, then killed it. Remove the fuse, start the car for 10 seconds again (it starts to splutter) then kill it.
When I went to release the pressure from the schrader valve, only a weak spurt of petrol came out (I stupidly didn't have any rags, and kitchen towel isn't really the best thing for the job)
This is the only angle I could get to work on removing the banjo bolt. A ratchet spanner would have been really handy
But I had to crack on like this, taking it slowly as not to cross-thread anything, making a lot of small turns. The 'leccy tape helps with stopping the M8 from falling down onto the undertray.
Once that's loose, as well as the other fuel line, pressure release valve and the T30 torx fixings, you can remove the HPFP and get to the follower. A bit of fuel may spill out when you remove the pump, so have the rags to hand.
This is what mine looked like. Car is on 73k, so I've got to assume that's how old this follower is.
And that's pretty much it. Put in the new follower, carefully line up the fuel pump and tighten the torx bits in stages so it goes in square, replace the pressure release valve and the fuel lines (start with finger tight, so you don't cross thread anything), sensors and finally the #27 fuse.
Prime the pump a few times by half turning the ignition key. Then start her up: as good as new