Following your links it seems that the kits seem to cost 60 to 70 pounds which does seem like a lot. Whether you think that is worth it will depend on your personality. Let's just give a brief overview of what you need and then you can decide for yourself.
The main bittering agent. You can buy old world hops like Saaz but they seem to be twice as expensive as the less high brow alternative and I doubt you will taste the difference. I Usually just buy what the beer supply shop has on special.
If you are following a recipe then buy the grains as need be. If you are going to explore your own taste then buy one kg of some grains that sound good to you and start to experiment. You only have to satisfy your own taste buds.
Just one thing you should be sure is to use a primary grain that has suitable diastatic power that is to say enough sugars will be expelled from the grain during the boil as to give the yeast something to convert into gas and alcohol. Do some research or contact your local supplier and see what they recommend.
Here again you can go deep and try liquid yeast but as what is the case with expensive hops you really have to have an immensely refined taste for it really to matter. One thing that does matter is to make sure you buy brewers yeast and not bakers yeast. Bakers yeast is much more potent but is also much less tolerant to alcohol which makes your brew much more likely to flop.
Yet again here you can go deep and try purified or mineral water but as a general rule of thumb if you can drink your tap water you can make beer with it.
Any 10 liter stainless steel pot will do.
Usually glass but any non plastic bottle that shuts tight can be used.
Beer shops should sell this but any cheese cloth or muslin bag will also do.
I like keeping grains and hops in separate bags during the boil because then I can use the grains for bread making.
There is also things like an auto siphon. Something that is used to get the
fermented wort from the fermentation vessel to the bottles without any chance of aerating.
You can use one I guess but I have poured my wort into the bottles post fermentation and have yet to see any real negative effects on the end product.
There is also things like a grommet and a airlock. This is used in your fermentation vessel to let the gas escape but not let any air in. This is good practice to use but there is other alternatives.
Instead of buying an airlock you can use a grommet in the lid of your fermentation vessel and also some food grade plastic tubing that goes from the vessel into a container of water. This is also a good way to let the gas out and not let any air in.