The legal drive limit is 35mcg/ 100ml in breath, or 80mg/ 100ml in blood.
A woman can have 3 units in a 2 hour period, a man can have 5 units.
Alcohol takes 20 minutes to get into your system fully, and then leaves your body at the rate of one unit per one hour.
In a white wine spritzer, if it contained 175ml of 12% wine that would be 2 units, if it was 250ml of 12% wine, that is 3 units (and beware, pubs serve most wine drinks in at least a 175ml serving, they never use the 125ml measures anymore, female friends of mine have had 2 glasses of wine, the pub served large 250ml measures, and they were way over the legal drive limit at 6 units)
So, if you had a large 250ml measure of wine, that would 3 units therefore would take 3 and half hours (including the 20 ish minutes it takes to enter system) to leave your system, technically you could drive on that, but would give it as long as you could before driving as it takes an hour for every unit.
But, puddycat is totally right, dont drink if you dont want to, particuarly if your driving. Even if you drank within the legal limit, and you got pulled over, a policeman could still take you to the station for a breathtest if they are not qualified to do a roadside test (any many arnt) and this would not be a very nice experience, totally not worth the risk.
Dont feel impolite, its your choice and they should respect that and concentrate on their own drinking!