I want to buy some fuel hose in advance of replacing the lot - I've no idea when it was last done & there is a bit of a fuel smell in the boot, despite the car apparently having had a new tank fitted not long ago.

Does anyone know what lengths I need to buy?

I think i've found the sizes needed:

3/8" (8mm I.D) - various places. Must be high temp for injectors/under bonnet.
1/2" (12mm I.D)- found in the boot.
Ialthough it's expensive I was going to get this stuff for the injectors at least, as it's rated to 257 degrees Fahrenheit.
Ethanol Proof Fuel Hose 8mm (5/16") - Car Builder Solutions - Kit Car Parts and Accessories

 

Make sure all the tank vent hoses are cleared: I spent a lot of money having the fuel tank replaced, the fuel lines from the tank replaced, then replaced again with copper piping, new boot carpet set and it still stinks of petrol when I open the boot lid because I am convinced that they did not blow through the vent lines and make sure that they were clean.
The tank has to vent somewhere and if the pipes are blocked then it vents into the boot (trunk).

 

Thanks to Grant, this is the info I got

Memory.

The large from the main tank to teh sump tank is 1/2" (12.5mm)
The large from the sump tank to the pump inlet is the same size.
The high pressure from the pump to the elbow in the floor is 5/16" (7.5-8.0mm).
The return in the LH corner is 10mm.
The others floating around are 8mm.
The 2 on top of the cradle, outside the boot, are 8mm, and should be included, coz many a fuel smell in an XJ-S is traced eventually to those 2 suckers.

The vent hoses at the top RH corner and up into the buttress, NO idea, I removed them and did away with that stuff, and vented the tank to the outside.

All those hoses except the HIGH pressure hose are standard fuel rated hose, BUT, I use EFI spec on all of them except the 1/2" gravity hoses, where I use standard fuel rated hose.