No you don't have to get a valuation. Most people would get a surveyor to look at a second hand property but that would be a structural survey. The banks valuation is just to make sure the house is worth what they're lending you.
2. Please make the heading of your question relevant Don't post a general heading such as "help !" or "Mortgage query". If you post a heading such as "Mortgage for separated couple", it will get a better response and will be much easier to find if you need to go back to look for it.