ditching the standard plastic Bosch parts for a pair of Forge Motorsport FMCL007P closed loop piston type diverter valves (with the yellow springs). Took about 80 minutes, but boy it was hot in there!
 

Open the engine lid:
 

Take off the intercooler cover and the intercooler itself:

Remember to hold the backs of these two bolts when you undo them, or you’ll lose the nuts:

Then cover the turbo pipes with latex gloves or similar:

Don’t start on this side:

Start by taking the airbox off instead, taking off the airbox cover, then take the air filter out, then undo the bolt at the top and undo the clip at the back:

And there, tucked away, is the dump valve:

Once you’ve undone the two hose clips with a 7mm socket you can pull the pipes off:

And here are the new Forge FMCL007P and the old Bosch part:

And here it is installed:

So switch back to the other side, and after moving the blower motor out the way a little, there it is:

I chose to undo one pipe from where it was, and the other pipe I couldn’t quite get to, so I undid it from the back of the manifold instead (under the throttle cables):

So I swapped the pipe from the old part on to the new part carefully, so the bends were oriented correctly:

And put the new part and pipe in place:

Then put everything back in place:

Remembering to take the gloves off the pipes before putting the intercooler back on!