Just for an update: My gas valve arrived last week so i started practising welding and i got the hang of it quite quickly. So i then set to work tacking up the bottom chassis rails, once i'd done that i decided to flip it over to make sure it was symmetrical....it wasnt. The 2 pieces with the massive angle on them were not the same, meaning it sat slightly over to the left hand side, i got all of that sorted and it is symmetrical now.
I've tack welded the front frame together now, after reading through chris's tutorial on it a few times i managed to get it all right first time
I've also started tack welding the uprights onto the bottom rails, its all starting to come together now