Marital status doesn't change a thing...in house-buying terms, I hasten to add.
If you buy a property jointly you won't be First Time Buyers for Stamp Duty purposes, but you will be for Tax Relief purposes, while your partner will only get FTB status for Tax Relief purposes for the balance of seven years since s/he first purchased.
I suppose there's one exception to this - if you can buy a home for yourself with no help from your partner before you marry, I think you would pay no Stamp Duty.