gbss.org.uk/
This website has a helpline OP, they are really good and can answer any questions.
The antibiotics are usually given every 4 hours. You have a canula which is connected to a drip to administer the antibiotics (canula can feel quite uncomfortable and obviously you've got to stay still while they fit it which can be difficult and stressful while having contractions)!
It can be capped so you can get in the pool but I think you have to get out to get next dose given. Different hospitals may have different policies so best to check.
I think even without antibiotics the risk of baby getting gbs is low (1 in 200) I think????
Risk factor also changes with different things such as if waters go early/labour early/if previous Baby has step b, etc.
There are also downsides of antibiotics, such as increased risk of thrush to baby which may be worth considering particularly if you are looking to breastfeed.
Have a good read of the risks and effects of antibiotics.
If you do decide you want them, make sure you arrive at the hospital in plenary of time as you will need them 4 hours before delivery to be effective and if hospital is busy you may have to wait for them to be signed off, etc.
Hospitals will usually want to wait until your in established labour or waters break.
Also worth considering - not allowing any internal examinations? This increases your infection risk. Have a read about other ways midwife can tell if you're in established labour.
Some hospitals will want to augment labour 12 hours (may be sooner??)after waters break. You may also want to research risks of this.
May be worth having meeting with consultant/senior midwife to discuss your options.