I think that you can be pretty flexible, I live in deepest Cumbria and I suspect my nearest Spaghetti Squash is London! Butternut is fine as a substitute. If you want fancy buy a spiralizer and make butternut noodle and things like courgetti with it. Quite frankly, life is too short to worry.. I just make cubes and eat them with what ever Im eating.
Meat is expensive.... I must say that Americans have it easy, with the price of things over there. Here I'm not prepared to spend too much on meat. I but a bit of grass fed on line from Green Pastures... Its not organic but they just dont want to have to pass the prices of an organic certificate on to customers. Its the best meat Ive come across. I "bulk" it out with local butchers meat as you can ask him where it came from. Round here its probably the field behind the house.
In a city... get to know a local butcher and you'll get better deal than the supermarket. Don't think that it is practical with meat price being £20 a kilo to buy organic grass fed here. Any lamb is grass fed! beef here too if you ask your butcher for it.
above all don't stress about having the right things in the house... there's always Aberdeen angus, good old fashioned lamb,rope grown mussels, prawns, scallops,cabbage, carrots,neeps and tatties! Why buy from half way round the world when Scotland produces magnificent food of its own?