I have spare leek seedlings ready to plant out now. Let me know when you want them and I will lift them for you. You will need 6-8 for each 1.2m row; plant one or two rows. I planted out mine last week on plot 248 - see the bed covered in mesh.  Let me know when you want them and I will lift them for you.

The RHS has a very good video on leeks.
https://www.rhs.org.uk/videos/advice/Leeks

I tend to plant out my leeks when they are much smaller, with no need to trim roots or tops, and into shallower holes - 6-8cm deep.  When the ground is dry it is a good idea to lever a small gap with a trowel and water into the gap; using a dibber in a drought is impossible but pre-watering makes it easier.  There is a dibber on the compost heap.  I also ignore the advice on needing lots of white stem.

I plant about 20cm apart in rows 30cm apart but I have the space and want large leeks in late winter.  Where space is limited and cropping is before Christmas 15-20cm each way is ok.

Charles Dowding offers an alternative approach, including planting less deeply in clumps and with no regard for getting white stems.
https://www.youtube.com/watch?v=CrqcUK2rdhw

The mesh covering is to try to avoid damage by leek moth.  I had much damage a few years ago so I now mesh from planting time until September.  There is mesh in a fabric bin in the 251 Shed.