Hummm! Is it too late to change your order? I would definitely advise a smaller wheeled folder.If you leave any kind of folder outside you'll eventually attract the attention of the light-fingered brigade. As others have stated 20" is about the best compromise (no folder can claim to be perfect, all my folders have their advantages and dis-ads).
Whatever you choose, give it a while, then get off one or two stops earlier and build your confidence and fitness, or get off halfway, cycle 1/4, stop at charming pub (take your bike in with you! You'll be chatting with the locals in two shakes), have a sherbet or two, then cycle final 1/4!
Also if you decide to cycle home, if it seems too much, make for the nearest station and jump back on the train! Easy
Don't get the cheapest waterproofs, make sure they are breathable ones.