Be wary of getting a taxi if you're working within a budget! I was on a strict budget and got a taxi from Dibden Manor to the airport earlier this year and it was upwards of £40. If I had more time I would've done what I did on the way there - train between Southampton Central - Airport (~£3) // bus between Southampton Central - Dibden (~£5)// taxi between Dibden bus stop (near Tesco) - Dibden Manor (~£8).