Code 75 is finer and more true to scale than code 100. Peco sell .adaptor rails (packs of 4) if you wish to join code 100 to code 75. I use code 100 myself on my 00 and HO layouts, and once weathered you do not notice the larger rail profile so much.
If you have a lot of old stock and don't want to re-wheel then code 100 is the way to go. At the end of the day day its really down to personal choice and what looks right for you
How many more Joko's do we need, we already have plenty of good 08/09's from Hornby and Bachmann. Now if you had done a class 81 .
To be fair, the lights were very poor on the real ones. (I should know having worked on them in the past ).