Before doing that, have a go at SSM's Wickham inspection car. At 27 Euros, it's not going to bankrupt you if you mess it up. All brass, so your soldering skills will be tested, but not complex.
Once you're satisfied it's gone together, I think the E/J26 will be ready and waiting for quite a lot of soldering.
Don't make the mistake that one past Forum member made of launching straight into the 800 class 4-6-0. He ruined it and it was a terrible thing to watch it happen. 170 Euros down the drain.