I'll do my best Tilly, I just do it - serves about 4 and I freeze any unused helpings.
Cut heavy green bits and roots off leeks (2 large or 3 small), remove outer layer, wash any grit out, cut lengthways, turn onto cut surface and cut lengthways again, then chop across into slices about half an inch wide. Peel spuds and cut into smallish pieces - about 12 oz., but it's not precise. Chop 1 small onion fairly finely. Use a couple of vegetable stock cubes (I use 1 veg. & 1 chicken) to make 1 and a half pints of stock.
Over a low heat melt a mix of butter (about 2oz) in a pan with some oil to prevent the butter burning. Add chopped leeks and onion and let the mix slowly soften and become translucent, stir occasionally. I find this can take longer that you would think, possibly 15/20 mins. ,which is why I make a lot and freeze it. Don't let them go brown. When ready, tip the spuds in, add the stock and bring to the boil until potatoes are very tender (I stick a fork in and if the potato breaks away it is fine). Season to taste (or as your doctor has ordered if you are on low salt).
At this point I use a hand blender to mush everything up a bit, whilst retaining chunky texture, and Robert is your father's brother! If you like 'cream of' soup then this is the point at which to add some milk or single cream, but a warning is that once cream/milk is added it does not freeze well.
Seriously, just relax and enjoy soup-making. I used to follow recipes slavishly, but you can make soup from almost anything. Left-over roast veg. make a tasty soup.
Hope this helps, have fun!