I have grown quite a few williamsii seeds from a mother plants that produces about 50 seeds per year, it's pretty hard to get them to germinate. Of those that do, even fewer make it past year 1. They are very difficult to get to maturity, (unless you live in a climatically perfect area for them, which England is not)
I have found the best way to get them into little pups is place them into a pot you are happy for them to stay in for a couple of years. I would not recommend transplanting them once they are pups, as almost every time I have done this they have died, no matter how careful I am. They are VERY sensitive to change.
Once you have spaced them out, cover them with about 5mm of well draining specialist cacti soil. Make sure it is not nutrient rich, they grow very very slowly, and don't need high nutrient soil or feeding for a couple of years at least.
Water the soil well, but don't soak it. Cover the pot in cling film (saran wrap) and leave it somewhere warm, with some sunlight, but not direct all day. They should come up in a week or so. Once you have a few little heads showing, cut into the cling film to allow some ventilation. Gradually increase the amount of ventilation until they are acclimatised, this could take some weeks, and is a black art to keep them happy!
Regards your situation, I'm afraid to say if they havent come up by now they probably will not at all, but you can try covering them and see if anything goes. Make sure you plant them at the right time of year for where you live as well.
Much easier than growing from seed is buying a few 5 year old cacti, and cutting the buttons off. Let them dry and place on soil to re root. The roots you cut will spring some more healthy pups, so you can double your stock every 3-5 years. They are also much more hardy when they are this old, so you don't lose as many!