Hi matey, I can offer you a few tips on the actual fitting of the WON nitrous kit as i've fitted their excellent kit i bought used off eBay years ago for my non cosworth turbo 16v engine.
Be extra carefull when handling the nylon feed pipes as they can kink easy and when cutting them to the correct length don't use tools such as pliers, snipers ect as they bugger the ends of the pipe, I used a very sharp Victorinox pen knife.
Olives are 1 use only so make sure you've correctly cut the pipes first then tighten the nuts to crush the olive. Try and use the 5mm newer fuel feed pipe available off the won site and get a spare pack of 4 and 5mm olives too.
If possible try and fit a backlit nitrous press. gauge inside the car, pref. on the dash if there is room, fat lot of good a gauge is when it's fitted on the nitrous bottle hidden in the boot..
When tightening the 4 or 5mm nuts always run a 2.5 or 3mm drill tip inside the nylon pipe as sometimes the olives tend to close up the pipe whilst tightening.
A bottle heater would be ideal to keep the nitrous up to pressure. If your running the original Garrett T3 with a .48A/R turbine housing that will definatly choke up, much better would be a .63 but you'll probably experience some turbo lag, bit of a compromise really.
ALWAYS read your engine's sparkplugs whilst tuning the mill for the first time, you can bugger all 4 pistons in a flash if it runs lean, a wideband is a must.
Try and keep the pipes that feed the won sprayer jets as equal as possible in length and remember to aim the small dots punched on the chromed bodies fowards, check also the height when fitting into the inlet runners. If your still using the original Weber ecu you could also use the ignition octane retard plug to back off a few degrees timing whilst on the gas, if needed.
There's probably more but that's more or the less the long and sort of it, for my experience anyway.
When you've finished plumbing in the system always open the nitrous to blast out any swarf or tiny bits of plastic that may be in the lines and check for leaks, have a look at the nitrous solonoid's small filter and change if ness.
If you get stuck you could always give somebody like Tony Mannock of Turbosystems a bell, he advised me and has a huge amout of experience with cosworth engines and nitrous, as do many others o Passionford such as Chip etc.
Good luck!!