It's no joke, Zone 1 is prime real estate, after all. Demand outstrips supply consistently. For something affordable AND spacious, consider looking further out. The travel cost might be worth the trade for a bigger living space. Plus, the London transport network is pretty solid.
Older houses come with their quirks, and drains can be a big one. Before you panic, might be worth it to get the house inspected—not just for the drain lifeforms but for any other surprises waiting. Better safe than sorry, especially when it comes to where you live!