honestly, i'm responding more to some of the advice you got before....
It is not time to wean until YOU decide it is time to wean. Do NOT listen to anyone who says "8 months is old enough to wean." cow milk and vanilla wafers is inappropriate for a baby of 8 months.
Babies of 8 months who are breastfed do not need much water. water is not going to help him sleep more.
More solids during the day is not necessary unless you feel he needs more, as breastmilk should be primary nutrition until 12 months at least.
Cereal to make a baby STTN is a myth.
If a baby STTN at 2 months old, yay for that baby. But that is not normal. it's actually ok if your baby is still waking.
More nursing during the day may help, but be aware that it is perfectly normal for an 8 month old to want to nurse during the night.
The book Babywise has been shown to be detrimental to the breastfeeding relationship. I can not for the life of me understand why people still push this book.
Tracy Hogg (the "baby whisperer") is on the fence about many things, but i found her "toddler whisperer" book to be offensive, when she said that toddlers who are still nursing are only doing so because the mom wants to continue babying the toddler. (WHAT?!?!?!) When I read this I knew that she was not very supportive of breastfeeding. I wouldn't be fond of the advice she would give.
A true pro-breastfeeding, non-sleep-training (because these aren't puppies we are talking about) author is Elizabeth Pantley, who wrote The No Cry Sleep Solution. She gives nice advice about nursing at night. Her book is one to look into. She also has a website with lots of support (just do a search for her name).
Co-sleeping really is wonderful for allowing the family to sleep. These days don't really last that long in the scheme of things, and will be over before you know it. If you are planning to breastfeed until 1 year (the American Academy of Pediatrics recommends 1 year, and then until both mother and baby still want, and the World Health Organization recommends 2 years) then a lot of the advice given is not going to help, and indeed will hurt, your breastfeeding relationship.
Good luck with the sleeping. It is hard, but filling your baby up on things that lack the nutrition of breastmilk is NOT the answer. WOrking in more feedings (or cluster feeding in the evening on demand) will work much better than filling his tummy with filler like cereal and water, which he doesn't need.