Did midwives leave G&A, delivery pack etc at your home beforehand?
I was told to collect a "home birth box" from the birth centre, and keep it at home for the midwives to use when they got here. I don't think it had entonox in it, think they probably brought that with them (not that I used it, midwife only arrived in nick of time when it was too late for gas and air).
I'd want a use a birth pool - what do you use to fill it? And empty it?
I hired a birthing pool but sadly didn't get to use it (all happened too fast) but it came with a hose, the hire company asked what type of tap I have to make sure they sent the right one. No idea about emptying sorry 
If the pool was downstairs and bedroom upstairs, where did you deal with 3rd stage?
I gave birth in my bathroom and moved to my bedroom next door. However, I had been planning to set up the pool in my living room and lie on the (covered) sofa afterwards. My bed was obviously bigger and more comfy and DH could snuggle up with me as well so it worked out better that way. If you had a big enough room downstairs, it could work well to put a mattress on the floor in the same room as the birthing pool.
Did you end up with blood all over the place, or did the midwives get pads etc down in time?
As I said, gave birth in bathroom, so all easy to clean - not that I cleaned up, the midwives did! They were very careful to lay out towels and incontinence pads to protect my bed and carpet, so there wasn't a lot of mess at all. We got a bit of blood on the sheets but but not much. I do have a waterproof mattress protector anyway so get one of those if you don't have one already - just in case of leaks or whatever.
Did they hang around for ages afterwards?
Not really, DD was born around 9am, then there's the third stage and I also had to have stitches (which they were able to do at home thankfully), they also cleaned up and then sat quietly downstairs doing paperwork (well not much paper, they had laptops I think
) just staying out of our way but on standby in case we needed them. I think they always have to stick around for a certain length of time after the birth and in my case they checked blood loss carefully and kept an eye on me for that (previous PPH). But all was fine and I think they left maybe 1ish? One of them came back later in the day to check on us again IIRC. I can't really remember can you tell 
The birth itself was fast and intense and I didn't quite realise how far along I was until I felt the urge to push - so I'm very glad that I planned a home birth and wasn't trying to rush into hospital, which would have been very stressful indeed. As it is, the midwives did the rushing 
Best of luck, hope all goes smoothly for you and you can be at home, as it's lovely if it works out 