The prices are estimated by contributors and meant only as a guide.
Budget = under £15 (per person, food only)
Moderate = £15-30
Splurge = above £30 per person

Budget

Giraffe - (Marylebone tube) Blandford Street
Chain.  Vegetarian options, also chicken. They have a special price from 5 to 7.  Great food, very casual. After 7, prices still considered "budget." They also have a great weekend brunch, served until 4!

[BUDGET TO MODERATE]

The Sea Shell - (Marylebone tube) Lisson Grove
Good quality (posh) fish and chips.

Eat and Two Veg - Top of Marylebone High Street
Close to: Regent's Park, Madame Tussauds
Vegetarian restaurant, has an American diner feel!
www.eatandtwoveg.com

The Golden Hind - Marylebone Lane
Fish & chip shop with reputation for being one of the best in London.
Beautiful old fryer, home-made tartare sauce.
Take-away or eat-in, but gets very busy. 

Moderate

[MODERATE TO SPLURGE]

Royal China - (Baker Street tube)
Chain dim sum (Chinese tapas/ meze). Only at lunch time.

SPLURGE