Hi Nappyvalley happy to have a go at explaining the ins and outs of IVF if you think it will help...and also, thinking about clinics, it might be worth looking at the results of your nearby clinics - if the Wessex one is booked up, it might be a good sign! The better the clinic the longer the waiting lists IMO - the best private one near to me in the north has a 2 month waiting list to see a consultant privately for the initial consultation.
To my mind, IVF works along the following lines (and different clinis follow different protocols so you may not get this) ...
Downregging - by injections/sniffing drugs/taking the pill - this phase is designed with the aim in mind of making sure you have the greatest number of mature eggs possible at egg collection time. To give you the best shot at this it helps to make sure your ovaries don't have any growing follicles to start with, as this could give you some mature and some immature eggs rather than all mature ones. So you need to take drugs to "downregulate" your ovaries and make sure there are no follicles starting to develop. This phase lasts around 2-5 weeks, depending on your clinic and you. IMO it also helps the smaller clinics, as if all the IVF patients that week are started off at the same time (impossible to synchonise this without downregging) then they can schedule the surgeon for one day's surgery doing egg collections, rather than having to do a couple every day.
After downregging you will have a baseline scan to check your ovaries don't have any cysts or large follicles (interfers with the stimulating drugs) and to check your womb lining is thin (the stimulating drugs make this thicker, so best to start with a thin lining)
The day after baseline scan, you will start taking the stimulating drugs to get your follicles, hopefully containing eggs, to grow. Clinics vary as to how often they see you during this phase of the treatment - could be scans and blood tests every 2 days, or only once or twice. One the follicles are getting big (over 20mm) they will go for egg collection. Then, as you say, put eggs and sperm together overnight to see how they get on, wait 2 or 5 days, pop the best embryos back and wait. During this wait you will go quietly mad, don't worry, it happens to everyone and that is what we are here for.
Your clinic will explain this far better, and also give you a handy schedule telling you which drugs to take when, as the timing of them is really important.
I enjoy lulling my consultant into a false sense of security, as they usually talk down to you about the science bit... I let them do this, then ask a really technical question (I have a degree in cell and molecular biology). Got to get your kicks where you can!
As for the drugs making you sick, it depends on the individual. Chances are you will be fine. I found the buserelin given to me for downregging for my first cycle put me in The Worst Mood Ever...but I was v busy at work, it was Christmas and I had 8 relatives coming to stay too. But since then I've used other drugs to downreg, and the stimulating drugs tend to cheer me up. Weight gain is a possibility - not a certainty though - and you might find you are less active than normal toward egg collection and during the waiting period afterwards until you test.
Anything else, just ask us. And don't forget this is just my take on it, others may have a better explanation.