CD- sorry to come to this so late - I've been in far Eastern Russia for a week. I've never experienced a 10 hour domestic flight before, especially on a Russain airline...
You know the mechanics of IVF from the thread. In terms of practicalities:-
Phone and get brochures from the main clinics:
\link{http://www.argc.co.uk\ARGC}, 13 Upper Wimpole Street, London, W1G 6LP, 0207 486 1230
\link{http://www.ivf.org.uk\Lister}, The Lister Hospital, Chelsea Bridge Road, London, SW1W 8RH, 020 7730 3417
The Bridge Centre and IVF Hammersmith are also good, but these are the top 2 in London for women in your age group. Have a look at the \link{http://www.hfea.gov.uk/Home\HFEA site} for more info - they break down the stats by age. However when you speak to the clinics ensure that you get their latest stats, as results do change over time.
Get any test results that you have from your GP and arrange a consultation with whichever one you like the look of, or both. Should set you back £200ish). Best money I've ever spent, especially after wasting 3 years on the NHS...
The consult will give you a lot more information and advise. It doesn't propel you into IVF automatically (though I suspect given your age they will put it on the agenda). You will come out very well informed as to what options you have. Most of the information can be worked out from websites etc, but if you have the cash I would pay for the consult.
Once you've had a consult then you can think and have counselling over what you want to do. You will just be very well informed as to what could happen.
If you do proceed with treatment there is a lot of going backwards and forwards for scans etc. And you'll need to be able to inject yourself with the drugs or otherwise find someone to do that and factor it in timewise. Choosing a location on the basis of ease of getting there is a good idea. I had one cycle where I had a 3-4 hour round trip every other day for scans. Not easy to hide that!
I went with Lister and found them to be very good. I fitted in all my scans at either 8:30 or lunchtime. From a work perspective the main issue is that you cannot be certain once you start a cycle as to when it will end, and you need to put aside a day for egg collection and a morning for them to put back the embryo (or 2). It is hard to keep your work diary that flexible, but you can feign illness! My workplace was very supportive and my boss knew, so covered for me when necessary.
Without being alarmist, every month counts, and there is a huge difference in the success results for 38-39 yos and 40-42 yos. I think for Lister it is a 25% success rate for the former and 15% for the latter. Of course the fact that you've got dd probably means that your personal rates are higher than these averages, but the age factor is a huge one.
I've had 4 IVFs at the Lister, and am very positive about them. It is a little bit of a factory approach (they have 7-12 egg collections each day, so along with ARGC are one of the busiest clinics), but the whole team were very good (and it is very much a team approach).
I think that the only other thing I would add is that it is hard not to get obsessive about the whole process. you will end up knowing more about your reproductive cycle than you woudl ever want to. It seemed very odd to be trackig numbers and sizes and follicles and hormone levels all the time.
Good luck with your decision