With a 1.104 beer, you are probably not going to get down to 1.02 and with the ingredients that I assume are in there you are DEFINITELY never going to get to 1.01 (without amylase or something, but that just wouldn't be right). Anywhere around 1.030 +/- 5 should be okay for that style.
You underpitched, possibly by a significant amount since you only made a 1 qt starter for that beer. I wouldn't worry about it, and just leave it in the primary for however long.
How long do you plan on leaving it in the primary? For a big beer, you want to do it longer than you would ordinarily because it's going to take longer or the yeast to eat all the sugars. They start to get pooped out after a while so I would do it at least 3-4 weeks. Unless you want to age it longer than that in the carboy I would just bottle it then also.
Champagne yeast isn't going to get it down to 1.01 either because it can't ferment maltotriose, like most other ale yeasts. It won't make it any drier than your London ale could (theoretically). The thing about champagne yeast is that it can survive in harsh conditions (high alcohol, low nutrient).