Random tips in no particular order of timeline or importance:
Have two bags - a labour bag and an afterwards bag.
Noise cancelling headphones - don't worry about not hearing your baby, the midwives will wake you up if you need to, but if you're sat there like piffy and really just want to watch loose women while you're trying to breastfeed it's worth it. Also download some netflix shows onto your tablet or your phone for when you can't sleep in the middle of the night.
More babygrows than you think you need - I ended up being in for 3 days and had to send DH home for more clothes because I expected to be in and out. I would certainly go for at least 5 days worth for baby to be on the safe side.
Don't bother with disposable knickers- they are as uncomfortable as balls. Go to primark and get some cheap granny knickers that you can bin after and it probably costs the same.
Borrow a pair of DH's pyjama bottoms - they will be good while you're waiting for your bump to go down. I can see why people want nighties but if you're up and down then nighties can be a bit... exposing!
Dark coloured dressing gown - Dunelm do them in black and dark navy towelling. Use it instead of a towel when you go for a shower- doesn't show the stains!
breakfast cereal variety packs - I really wanted coco pops after I'd given birth. The NHS options can be a bit limited. Snacks in general are a good idea- I was paralysed from the waist down and they kept forgetting to feed me. DH had to bring me a panini from the cafe.
Super concentrated squash drops - again it's nice to have the option of something that isn't water or tea.
Lucozade tablets (get them from the chemist) - good to give you a burst of energy in labour. Lucozade drink have replaced half the glucose with artificial sweeteners now so they are garbage. The tablets are orangey flavoured and just taste like swizzels sweets.
A travel sized mild mouthwash or some gum - you will probably vom in labour. This will make you feel better.
Clary sage essential oil - put some on a hanky or a facecloth and huff the fuck out of it when you're having a contraction. It's magical.
A jug - you can use it for someone to pour warm water on you during labour (if you use a bath or birthing pool) and you can use it afterwards to pour cool water on your fanny when you pee to stop the burning. I got a squishy bath one we still use and it squashed nicely into the bag
Something to read/do- I really wish I'd had some puzzles to keep me occupied.
Hair bobbles - because of the aforementioned vomming. Also the sweating etc. Labour ain't pretty.
Travel hairdryer - buy a new one and bring the receipt - if they try and tell you you can't use it because it needs PAT testing that doesn't apply to new products.
Maternity pads - I think they are a bit weird, and I don't think that special maternity pads do a better job than ordinary night time pads, plus they're really narrow and they tell you to wear two anyway. Don't get Always or tena lady though because of the weird gel. Bodyform were alright.
Bring some scented swing bin liners to put your washing in. Bring a few and then if you're in for longer DH or whoever can take them home after they visit. Scented is good because they could have allsorts of bodily delights on them.
Also, I can't stress this enough, WRITE. YOUR. DAMN. BIRTH. PLAN. In great detail. Keep it with your notes - if you want to type it on the computer make sure you staple it into the notes booklet so it can't get lost. Decide what you want to do in all the worst case scenarios, how you want to be told, who makes decisions, all of that. All the friends I've ever spoken to who felt they didn't have a choice didn't have a very detailed birth plan. If none of those worst case scenarios happen then great! If any do, then you need to have decided what you actually want while you're not loopy on hormones, painkillers, pain, adrenaline, no sleep, no food, yadda yadda.
That's all for now!