Are there any bottom end recorders that I should positively avoid?

The best makers for low-end stuff are Aulos and Yamaha; Zen-On for slightly more expensive things (their altos are great). Dolmetsch (aka Kent) are not very good. Hornby and Early Learning Centre stuff is total crap - made to sell to parents who don't know anything about what they're buying for their kids. Aulos and Yamaha recorders are so easy to find there's not much reason to look elsewhere for a starter instrument.

The price list at Saunders Recorders is annotated with opinionated mini-reviews which give you a good idea of what to think about. The guy who runs that shop is very clear about when an instrument is value for money and when it isn't.