The swob is done after a recent encounter, its more accurate earlier than a urine test. Ive had it done a few times, its no big deal, take a deep breath and its over in seconds. Stings like feck yes, but its ok. Basically they look at it under a microscope there and then in the clinic and can see any bacteria or signs of inflammation.
With regards home testing kits, i've also used Better2Know. For £40 they send out a ghonn and clym testing kit the next day. Pee in the pot (first thing in the morning is best), pop it in the supplied packaging, and into a post box. You get a unique login code for the website and the results appear there in 3-4 days.
Thats if you want to not go to the clinic.
Only other thing with the NHS clinics is that they take around 14 days to text you the results. The bloods are usually done in 3 days, urine culture longer, about 5 days, a swob can be 10 days to culture it. But generally you'll wait 14 days.
Private clinics like SameDayDr , Better2Know are expensive, but, you can get results the same day or next day.
As for swobs in the mouth Strawberry - you prob know you can have those infections in the throat, and downstairs, and the only way to detect the throat one is from the swob. The human body can kill off the bacteria in the throat, it can take about 3 months, but its possible in that time to give it to someone else via a blow job.