Hi everyone, my baby boy has arrived safely! 
He was born on Thursday morning after a fairly quick but dramatic labour (not the lovely serene water-birth I'd had in mind and I certainly didn't care about mood-lighting or forest scenes on the walls once labour was in full swing 
)...
I had braxton-hicks on and off all Wednesday then around midnight they suddenly got very very painful so I got DH to time them. Most were 5mins or 7mins apart and the pain was getting hard to cope with so we phoned maternity assessment unit who said the pains sounded 'erratic' and advised us to stay at home as long as possible as they were very busy and we'd be sent home if not in active labour! Within half an hour my contractions were 3mins apart and I had excruciating back pain, so we went to maternity assessment and got sent to waiting room for ages (without being examined!) When they eventually took me to a cubicle they found I was 6cm dilated! I was in agony and starting to panic a bit, but they said there were no beds free on labour ward so I'd have to stay in my cubicle until a bed became available! Aaargh! Nightmare. There were 5 other women in the bay, all with partners staying, none of them in labour and the woman in next bed kept calling out encouragement 
. So no privacy, no pain relief other than gas&air, and I was told to stay on the bed not walk around.
When a room finally became free I was transferred, midwives said baby was back-to-back which explained why it felt like my pelvis was breaking and why I had urge to push too early. After that things progressed quickly, though I was scared and totally unprepared for the level of pain and thought I couldn't do it. I was also vomiting every 5-10mins despite anti-sickness injections, was dehydrated and started hallucinating at one point. Only bearable position was kneeling up on bed with DH holding a sick-bowl and alternating the bowl with the gas-and-air and a glass of water (i kept missing the bowl but was beyond caring). When it came to pushing it felt impossible and seemed to last forever, baby had his hands up by his ears so when head crowned he got stuck and they made me change position. I felt top of his head between my legs and started screaming 'it doesn't fit' and midwife got a bit panicky too, she was calling for lignocaine to do an episiotomy, but she didn't have time as with next contraction (and a lot of effort from me) he was born! And it was amazing. He was all slippery and wriggly and crying loudly, so I picked him up and held him while they waited for cord to be ready for DH to cut. The pain vanished and the vomiting stopped and everything became so calm! Amazingly I didn't need any stitches either. Baby breastfed straight away and after short stay on postnatal ward we came home last night.
Ladies who are still suffering, please don't give up hope, HG really does pass and it's all worth it when baby arrives. I was in despair so many times with HG, wondering how I could go on, how I could cope, I felt like it had snatched my life away. But it was worth it! I thought I'd feel rough for a while after the birth and that the sickness might take a while to lift, but the transformation was instant. The nausea vanished, I can eat and drink normally, the heartburn and SPD has gone too. I don't even feel that tired... I was up so frequently in night with sickness and SPD that getting up to feed and change nappies and have cuddles with my gorgeous baby feels easy by comparison.
Thank you so much to everyone on this thread for their amazing support and patience, their advice and companionship. Special thanks to Lucinda, Meerka, MotherOfPearl, Elizabeth'sMum and all the other kind ladies who tirelessly support others through HG and give people hope when they're at their lowest. I don't know how I would have got through this pregnancy without you!
Good luck to all the ladies still suffering and I hope you find relief earlier than I did, remember not everyone suffers all the way through. Do push for better meds, rest as much as possible and use this thread; people here really understand what you're going through.