pak choi

You can certainly grow it in an unheated greenhouse if you sow now.  Not sure about outside - I think most of the stuff grown in the UK is done under poly tunnels.

It does much better in the autumn for me than at any other time of the year.

thanks Guys for your replies I will be sowing the seed asap and I must remember not to transplant Il leave them in the pots to grow on and yes they will be left to grow in the greenhouse or poly tunnel

FWIW, my sister and her husband (who live in Indiana, much colder than here, and similar or colder winters than much of the UK) grow Tatsoi in their outdoor garden in winter.  Tatsoi is the same species as pak choi (or bok choi), just a different variety.

I'm planting Tatsoi here this year, outdoors of course.

Yeah much less. It also likes flowering with lengthening days, so it's easier to grow in autumn than spring, although you can still try that from an early sowing. Mine are currently getting destroyed by slugs though

Something fun to try (it works and produced decent pak Choi for me).

If you buy it at the grocery store, after you use the leaves and petioles (leaf stems), the main plant stem is left. Put that in a plastic bag or container, place that somewhere inside out of the sun.  It will start developing growing shoots and roots from the base of the stem. After that, bury the whole thing point up, just below soil surface.

Most times, it will start growing again. I did this early this year, got a really good pak choi. Plenty for a stir fry, beautiful tasty leaves and stems.