Good idea to take a little step to help you get in and out (the type toddlers use to reach the loo) is good, as they can be quite high, and you are not at your most adaptable. Also a blow up bath pillow is good for leaning on. Flannelto wipe your face with, as I found the temperature feels quite hot and water or apple juice so you don't dehydrate.
I had a water birth with my second, and delivered in the water although midwife and husband wanted me to get out, used gas and air.
With my third I again used the pool (I think it makes a remarkable difference), and had to get out to deliver because I had a swollen cervix, but all okay. Again used gas and air.
I agree that there is not always midwifes who can deliver in water, but even if you use it for pain relief it really helps, and keeps you calm as you can float out inbetween contractions and get into so many more positions.
Don't know much about pain relief, but I cannot see why they wouldn''t let you do what you want, although once you do any of the above you cannot get back in the water.
The other thing they don't like giving the injection to get the placenta out quickly whilst you are in the water, so if this is important to you, let them know you want it as soon as you get out.
Hope this all makes sense - hope it all goes swimmingly!!