Prenatal vitamins and pre-seed?

Brandi-lea • Khaleesi-May Dizney Van Vliet - my precious daughter born on 23.6.15 👶🏼🌸
Looking to order some prenatal vitamins, just wanted to ask a few questions before I order a batch off Amazon- 
​1) are they expensive? (Uk price)
​2) can I take them whilst ttc?
​3) how will they help me get pregnant? 
​4) which are the best brand to buy?
​ALSO!
​Has anyone used pre-seed when ttc? Is it good? 
​Comments would be really appreciated!