Thanks for the heads up, just went and ordered some new fronts
 

My 3S has been removed and pulled apart and we confirmed that everything else (apart from the main caps and associated main bearing) looks completely perfect, so I could've just done the billet main caps and kept everything else the same. However, because of all the labour required to get to that point, I'm still going to take the opportunity to change to a 5S bottom end. Yesterday we sourced a 98+ 5SFE from which to take the block and crank. It's exciting to finally see some progress!

Hello throttle response! :-)

Now that you're changing to the 5S block and crank, what flywheel are you going to use. I assume you have the OEM flywheel. Did you decide to go aftermarket (such as Fidanza) or are you getting the holes in your 3SGTE flywheel elongated?

My OS Giken twin-plate clutch came with a flywheel. I'm not sure if it already has elongated holes.

The following parts have just been ordered from the US:
 
ATS Racing custom-ordered Wiseco 5S pistons (87.5mm, ~9:1 CR)
Pauter 5S Rods
ARP main studs
ARP rod bolts and head studs ('625+' upgrade, ie. the strongest available)
Hux Racing head stud support washers/hats
Hux Racing billet steel main caps
King race main bearings and rod bearings
ATS Racing 5SGTE MLS head gasket
New genuine water pump
New genuine high-flow oil pump
New genuine timing belt
Low-temp high-flow thermostat
5S flywheel bolts
5S rear main seal
Moroso oil pan

That'll be a tough motor Rob :) I'm not up to speed on what that combo can handle. 800+WHP?
 
Are you staying with the current turbo with the 10% greater displacement (faster spool) or moving up a size?

This combination of parts is virtually the strongest you can get. 
I'm probably going to stay with the GTX3076R turbo and enjoy the improved spool, but with these parts the engine will support more power than I could ever want if I changed the turbo in the future (even if that never happens, it will be reassuring to know that I have a higher factor of safety than before). 
After looking at this https://www.perrin.com/blog/post/garrett-gtx-turbo-comparo-part-2 the GTX3582R becomes very tempting because it would have identical spool (thanks to 2.2L vs 2.0L) while allowing 500+rwkw, but I think I'd rather have better spool than what I have now. Also, it's easy to forget that the stock e153 gearbox may not be able to handle significantly more than 400rwkw.

I miss my car!
It's now been 8 weeks, and ATS in the US are still waiting for the pistons to arrive so they can ship everything over.
 
I've been talking to Advance in the mean time, and it's likely that I'm going to proceed with twin in-tank staged fuel pumps, so I can have a good safety buffer rather than using up all of the available flow with my power level on a single Walbro E85 pump.
I'd like to upgrade the fuel return line to at least -6AN braided teflon hose (instead of the small stock return hard line on top of the tank), which will require the tank to come out anyway...hopefully for the final time!
 
I came up with my own custom strategy for controlling both fuel pumps, and I implemented it in my ECU last night in preparation. Here's how it will work:
- Each fuel pump will have its own relay controlled by separate ECU outputs
- Only 1 of the 2 pumps will run most of the time, until the flow of both pumps is required
- Every 5 minutes, the ECU will swap to the opposite fuel pump (but it will only do this in the over-run fuel-cut condition, so I won't feel it at all)
- By alternating the pumps periodically during cruise conditions or idle, I'm more likely to know if either of the pumps has a problem before the next time I intend to use all of the engine's power, in which case both pumps will need to be working correctly to achieve the expected fuel delivery
- Rather than having only a boost threshold setting for turning on both pumps, I thought it would be more ideal to turn on both fuel pumps based on the actual injector fuel-flow requirement exceeding a configurable value (my ECU already knows the litres per hour of fuel required by the injectors at any time, so it makes sense to utilise this information instead of just the boost level)

Some really nice bits you have ordered. Will twin pumps and their intake filters all actually fit through the hole into the tank?  Enlarging that pissy little steel return fuel line is definitely a good idea.  Have you considered access to fuel pump aperture via cabin at this time? A strategically positioned hole very carefully cut in the tunnel with a shaped plate secured by at least six bolts to spread the loads. We have no way to know what loads are involved in that tunnel area so it would need to be done properly.
Do you already have a gauge to monitor fuel pressure?