My car has been sitting for 2 years, it's MOT is this Monday.
I drained the old fuel out and filled with 5L of tesco 99 and a whole bottle of redex.
The theory was to run the strong redex solution through for 5 minutes, switch off for a day to let it do it's stuff, then repeat.
My question is.... Will too much redex effect the emissions test in a good or bad way?
There is a petrol station next to the MOT station, so I could easily fill up.... But should I?

Archie. Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

I did exactly the same on a petrol engined car and it failed on emissions, never had failed before.
Ran the car until the fuel tank was almost empty and then refilled. Retested with no other work and the emissions were well under the requirement. I put it down to the Redex at the time.

Ah, so I should remove all the redex then.... Not really a problem as there is maybe 3L left in the tank.
 Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

If you only have 5 litres in the tank with some redex i would let the engine idle at a slightly increased RPM, maybe 12-1400rpm until it runs dry.

That will flush most of it out of the system ad then just put the fresh stuff into the tank, -10litres should be enough to dilute any remaining parts on the fuel system out and the higher revs will help clear out any built up crud from the engine. Italian tune ups are known to be very good for diesels and seemed to work on my old cars as taking them straight in for the MOT slot with a nice HOT CAT seemed to help  FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.