YCombinator Startup School heavily emphasizes leaving your day job and committing 100%. I'm trying to start something similar to your Come Dine With Me, but out in public instead of at people's house. (plug: https://www.thawd.net coming to Seattle soon!) Devoting 100% of my mental energy to it means I have been able to iterate on the idea itself quickly, spend time talking to people about it (which is itself exhausting!) and completely engulf myself in the startup community.

There are people who devote 100% of their mental energy to whatever they are doing right now. Those people are not going to be successful with side projects. When I am building something, it is on my mind 100% of the time, waking up, showering, getting dressed, driving, eating, all the time.

I cannot do 2 projects at once.

In regards to coding, being a good programmer is only a small part of running a business. Marketing, managing a team, working with designers, and inspiring others with your idea are all skills that are incredibly important.

The code needs to work, sure. And hopefully it is reliable, but just as important, the business needs to work. You need to be able to send cold emails, handle rejection, and be able to put a smile on your face on demand at any time of day at any place meeting with anyone.

Of course before you quit your day job, make sure you have an idea that people want. Throw some marketing $ at it and see what your conversion rate it, even if it is to a "sign up for more info" form.

Go out and talk to people on the street, one of the most difficult things I did, which was step 1, was literally go to different neighborhoods, walk up to people, and ask them about my product idea. Especially for mass market products, this is a quick, and painful, way to cycle through ideas really quickly.

Also, for your email address extractor, have some sample input there. It'll go a long way towards explaining your value prop.